9th Feb 2011 

The Most Informative Q&A Site covering nearly all complexion flaws

By: Dr. Pierre

Questions & Answers On 
Sun Protection Factor (SPF)

Image of Premature Aging skin

Photo-damaged Skin 

This 69 year-old man has a photo-damaged skin, known as dermatoheliosis, on the left side of his face that has been exposed to the sun for 28 years as a truck-driver, and has suffered considerably on the left than his right side. The effects of the UVR have caused extreme premature aging. 

Images of Skin cancer 

Skin Cancer 

I am proud to be the pioneer in the R+D and the launching of the world’s first Anti-UV day cream in 1982, and with only SPF 8! 

Our rivals were quick in their attempt to outdo us and outdo one another among themselves by launching their own versions with ever increasing SPF, and at one time even boasting of an SPF120 product in the U.S.! 

As far as I’m concerned, I have done my rigorous R+D and I know that my SPF8 day cream is the best and the safest, and I stayed away from competing with my rivals in their wild SPF chase. 

My SPF8 creams (Product #s 70, 070, 74-P, 76-P and 79P) with a 200-minute protection all work by bouncing off and deflecting the UVR, leaving no chance for the UVR to accumulate on the skin and radiate into it over time.  

Higher SPF creams all work by filtering the UVR, but still leaving it to accumulate on the skin only to penetrate the skin eventually via radiation and leading to delayed pigmentation, pre-mature aging and a high risk of contacting skin cancer! 

This is one primary reason why sun-loving people usually look at least 10 years older than their real age, and why the Aussies has the highest skin cancer population rate in the world despite embracing the use of high SPF sunscreens. 

The accumulated UVA rays result in thickening of the epidermis and stratum corneum, as well as destruction of elastic fibers. 

So higher SPF means higher risk and more harm, and not the other way that they want you to believe! 


Dear Pierre, I read some of your replies in the Q&A sections and I must say that you are such an expert on skincare in the internet.

I wish I had found your beauty box much earlier.

I really need your help this time.

(1) I am a devoted user of sunscreens.

The other day, I read an article saying that "if you're using an SPF 15 moisturizer under an SPF 8 foundation, the protection you end up with may be about SPF 12 due to dilution".

If someone uses a moisturizer (without SPF) and an SPF 20 sunscreens, does it end up to be only SPF 10??????? (2) What is the sequence of applying physical and chemical sunscreens? Should a physical sunscreen be applied under or over a regular chemical sunscreen? (3) As regards maximization of UVA protection, will the sequence of layering in (2) be different if chemical sunscreens of Parsol 1789 is used together with another physical sunscreens? Please help! The hot summer is here already.

Thanks & regards, Kim (submitted by alias: KIM)

Yes, that's right if you apply both on top of one another immediately without waiting for one to dry up a little - that's quite a close approximate.

That's because the amount of concentration of the anti UV ingredients in the cream is the primary determinant of the SPF value.

So when you mix up one with SPF 15 and 8, you get the average of SPF 12.Example: if you have a gram of sugar mixed in 50 grams of water in one cup, and another 3 grams of sugar mixed in another 50 grams of a separate cup.

Now each cup will have different degree of sweetness, the latter cup being sweeter.

If you now mix the two cups of water, they will now be 4 grams of sugar in 100 grams of water, or 2 grams of sugar in 50 grams of water.

And 2 grams of sugar is exactly the average of 1gm + 3 gms.

So, the sweetness now is between the 1st cup and 2nd cup.

If you apply one over another immediately when they are both still liquid, and mixed them up on your skin, there isn't going to be much of a difference for which one to be applied first.

But if you apply the chemical sunscreen first, and wait a while for it to dry up, before applying the physical sunscreen, then this is preferred.

The chemical sunscreen works by absorbing the UV rays, to prevent them from penetration, but by absorbing the UV rays, the rays are accumulated and left on the skin surface.

This can be harmful over time.

The physical sunscreen works by reflecting & deflecting the UV rays, thus without retaining the rays on the skin surface.

So, it is better to reflect off the UV rays on first contact with the skin, rather than to allow the rays first to be absorbed and retained on the skin surface, in which case the inner layer will not be able to effectively reflect the rays.

The above suggestion is presumed that the person is not sensitive to chemical sunscreens.

The higher SPF value in a chemical sunscreen, the higher the risk of its sensitizing effect on skin, which can cause redness and swelling.

Parsol 1789 has been found to be a safe chemical sunscreen agent.

So the difference is that when it is applied as the first layer(that is in direct contact with the skin), it is very unlikely to cause any sensitizing effect on the skin.

If applied as 2nd layer it will still absorb UV rays and retain them on the skin.

Generally, sunscreens with very high SPF value, will have to primarily depend on chemical UV absorbers, and this is harmful.

Physical sunscreens use only very little chemical UV absorbing agents, but more physical UV reflection agents, and thus they are much safer.

It is better and safer to use a lower physical SPF cream, and wipe off and apply more often, than applying a high chemical SPF cream and left on the skin for several hours of exposure to the sun.

It is reported that the UV rays absorbed and retained on the skin for a long period of time can lead to pre-mature aging and skin cancer too.

Hope the above helps.

Regards: Pierre  

I am 27 years old, Japanese and living in the States for 6 years.

My acne has started since when I was 14 or so.

(After I started my period.) Although my acne on the cheek is gone, the openpores and redness remained and the skin got rougher.

And the worse thing is the part is expanding year by year.

As I mentioned before, before the menstruation, I get tiny acne inc. whitehead on the area where I don't have acne before.

So now clear skin is almost gone from my face.

I am sure I usually have whitehead as well as the blackhead.

(I cannot squeese unless I use needle.) I have whitehead near chin and neck now.

I know it is something to do with my hormone.

So I have started to take birth control pill called Oarth Tricyclen.

It is less than a month so that I cannot figure it has been good for me.

Before I took different kinds of antibiotics, Minocyn or monodox, but didn't work.

I also tryed topical products such as Metrogel, Azlex(New brand), Neostrata, and all kinds of stuff I can get from drug store.

Only tings I haven't try are Retain-A and Accutane....

I am not sure if you are familiar with those products...

I am single, not pregnant.

I usually use facewash from salon, which is Dermelogica "anti-back face wash" or Japanese CAC (Brand) powder type, this one is very mild.

For the toner I use Pola (Japanese) Sekkisei, or Chanel for Oily skin.

Lotion and sun protection I am using Total Diffence from Chanel (Spf 15, non-fre, oil control).

I try not to use fregrance-in, and avoiding oil contained.

I don't usually put makeups.

Night time I am not using anything right now except Vitamin E oil for aroud eyes and neck.

I used to have very oily skin but it is changing.

So I have kind of oily skin but it is also on the cheek.

People usually tell me I got very sensitive, or combi, or oily skin.

Aroun my nose and cheek, I have openpores and I can see oily-white stuff ( Are they comedos?) coming out from pores.

Sometimes I use twizler to take or they can be squeezed out.

I don't have Stress that much and I can sleep soon after I am in bed.

I think since I started to take birthcontroll pills, I sleep well.

(But I have very hard time waking up, maybe because my body has been changed as well as the bloodpressure.) I also take vitamins, eat a lot of fruit, vegis, and don't eat greasy that much.

I wash my face twice a day.

I went to see many dermetrogists and, some told me my problem is genetic, but non of my family has this proble that I know.

I even went for lazer because of the spider vains.

The doctor said, most of the redness is caused by acne.

So I have combi of things going on my facial skin.

But my acne is almost unseen (They are looked more like rough skin because they are small and not really poped out most cases)) with the redness.

Well, when I take picture closeup of my face I will send it to you.

Meanwhile I just want to try your products.

I forgot to tell you that I use mask, Purifying Mask from Shiseido and Chinaclay mask from Clentel (U.S. product).

I hardly use scrub since I know it might cause more broken vassels.

Please give me suggestion, I will do anything for my skin.

Thank you very much for taking your time.


(submitted by alias: Sachiko)

Hi Sachiko, I received your letter and 8 photographs.

Observing from your photos(although not very sharp), your skin is now very sensitive and inflamed.

You also mentioned that you flushed easily even since childhood days.

This means you have got very fine(and fair/light) epidermis.

As such, your skin is quite easily reddened also by sunlight(photosensitive), because your skin contains little amount of melanin pigment cells(melanocytes), and thus cannot effectively protect it from the harmful effects of the UV rays, which worsens your current condition.

Although you need protection from the sun (especially during summer time, or whenever you are out in the open), unfortunately it's not advisable for you to use sunscreen of high SPF value.

You should use only below SPF15 (try a small amount on your neck area first to test if your skin can take it or not).

You should also not use any soap-base cleansers(like the face wash you mentioned) to wash your face, and you should not wash more than twice a day for the time being.

Soap-based cleansers will cause superficial dehydration(though temporarily).

When this happens two events would follow:  

1. The skin cracks and ruptured(and became coarse), and allows bacteria to penetrate freely.

This worsens your acneic condition.

2. Your skin will physiologically react on its own to try to compensate the loss of moisture(due to the temporary dehydration caused by the soap-based cleanser).

When this happens there will be excessive production of sebum underneath your skin, causing your pores to clog.

Soap-based cleansers also contain salt(part of the ingredients to help increase the viscosity of the cleanser) which contributes to the hardening of the sebum.

Cream cleansers are generally better for conditions like yours, but some cream cleansers unfortunately contain large amount of high viscosity wax.

Such cleansers usually leave stains of hardened waxes on skin after rinsing, and thus also contribute to pore-clogs.

Cream cleansers with low viscosity wax and oil are known as non or low-comedogenic and are safer and more effective.

The same applies to day cream and night cream which are to be left on the face for long hours.

Those containing high viscosity wax and oil should be avoided.

You can do a simple test to find out if a cream(cleansers, day and night creams, etc.) is non-comedogenic or hyper-comedogenic (Non-comedogenic means not prone to contributing to comedo).

Just decant one to two ml of the cream and place it on a piece of normal writing paper for one to two days, and observe again (do not spread the cream. Just leave it as a lump like a small molehill).

If, after two days, most of the cream had disappeared and are absorbed into the paper(you can see the oil patch surrounding the cream), leaving very little or no traces of any visible cream on the paper, then the cream is low or non-comedogenic. 


If, on the other hand, you find the small molehill of cream is still there or has shrunk only slightly, leaving a lump of hardened wax substance, then the cream contains a high content of wax substance and should be avoided.

Too much of Vit E and Retin A will cause your skin to peel often(not good for sensitive skin like yours currently).

Clay mask will also absorb(suck) moisture from your skin and cause dehydration.

I recommend you stop applying for now.

Now I'm going to recommend you a simple regimen, using only four of our products first.

You should stop all others in order to see speedy results.

The 4 products are:  

1. Dr Pierre Product #17/F DeepCleanse Refreshening Fluid.

(This is a liquid cleanser/makeup remover).

2. Dr Pierre Product #69 Licorice Toner.

3. Dr Pierre Product #87 Azulene Active Cream.

4. Dr Pierre Product #090 Wondergel Ginseng AC Cream (Anti-Acne Cream).

Please follow and adhere to the following instructions closely:  

A) Every morning:  

Step 1 : Decant Prod #17/F on a cotton pad, and wipe face and neck gently to remove staled grease, dirt, dead-cells and any debris.

Step 2 : Rinse thoroughly with running water(Use a facial sponge if desired, but wipe gently and lightly).

Step 3 : Tap dry with a tissue(avoid using towel for time being).

Step 4 : Apply #69 with a cotton pad, by tapping lightly on face and neck, and wait a while for it to dry and to be absorbed, before going to the next step.

Step 5 : Apply #090 sparingly on acne spots(or acneic areas).

Apply #87 on all other unaffected areas.

For the time being, please avoid applying any makeup(except eyebrow and lip areas).

B) Every Evening/Night: Step 1: Decant Prod #17/F on a cotton pad, and wipe off makeup first(in your case eyebrow and lip areas only, if you do apply), then wipe face and neck gently to remove staled grease, dirt, dead-cells and any debris.

Step 2 : Rinse thoroughly with running water(Use a facial sponge if desired, but wipe gently and lightly).

Step 3 : Tap dry with a tissue(avoid using towel for time being).

Step 4 : Apply #69 with a cotton pad, by tapping lightly on face and neck, and wait a while for it to dry and to be absorbed, before going to the next step.

Step 5 : Apply #090 sparingly on acne spots(or acneic areas).

Apply #87 on all other unaffected areas. 

Other Hygiene/Health Aspects to observe:  

1. Tie your hair up when sleeping to avoid bacteria from hair from spreading to your ruptured skin.

2. Change your pillow case as often as possible - preferably cover it with a clean towel and change it daily.

3. Wash your hair daily if possible(avoiding the shampoo from flowing down on your face!!!).

4. Avoid squeezing, fiddling and pricking your acnes(or face) with bare hands/fingers.

5. Avoid the sun.

6. Avoid fried food.

7. Drink plenty of plain water.

8. Go to bed on time and sleep at least 7 to 8 hours nightly.

Do not stay up late at night.

9. Avoid dusty places or places near chemicals, where chemical gas/fumes are likely to be present.

Above steps are also applicable for your hands and other parts of the body as well.

Samples will be sent to you this week, and you should receive them next week.

Keep in touch with us, and let us know of your improvement, or if you have any further clarification to make, please don't hesitate to email me.

Best Regards: Pierre  

I have a Question. 

Isn't a suntan just a precursor to a sunburn? In other words, wasn't every sunburn a suntan a few hours earlier.

What does suntan lotion do? My theory is that it does nothing more than lengthen the amount of time before everything happens.

If you would get a tan in 40 minutes and a burn in 60 w/o lotion, then wouldn't putting on #2 just make it take 80 minutes to tan and 120 to burn? Please help me.

If you have a web page i could reference it would be great thanks cameron  

(submitted by alias: Cameron)

Hi Cameron, A suntan may usually appear as a precursor to a sunburn, but not always, and not under all circumstances.

The sun's rays comprise a portion of spectrum classified by scientists as Ultra-Violet(UV) rays.

These are further divided into UV-A, UV-B and UV-C.

UV-C is mostly shielded by the earth's ozone layer, leaving UV-A and UV-B to penetrate our atmosphere.

UV-A penetrates both our epidermis and dermis skin layers.

Since the basal layer(the last layer) of the epidermis and the prickle-cell layer(the first layer) of the dermis both contain melanin cells(melanocytes), these two layers of cells are stimulated simultaneously by the UV-A rays to produce more melanocytes - a natural chemical reaction ingeniously created by our God Almighty - to prevent the harmful effects of the UV rays against the underlying cells.

In other words, the hyper-production of more melanin (melanin means black) cells is to provide a more opaque skin layer(which otherwise would be more translucent) in order to obstruct penetration of the UV rays.

It is for this reason (that is, two layers of skin containing melanin cells being stimulated to multiply melanocytes simultaneously), that UV-A causes sun-tanning.

Tanning-beds in beauty salons also emit UV-A rays to produce quick tans.

However, the energy in UV-A is weaker than in UV-B.

That is why the tan doesn't last long (usually disappeared after one to three weeks), and that is also why UV-A doesn't cause sun-burn on its own.

On the other hand, UV-B's energy is much greater than UV-A's, and thus, it causes the burning sensation very quickly.

However, the penetration level of UV-B is only up to the epidermis.

Thus, UV-B causes only the epidermal layer(that is, only one layer) to multiply the production of its melanin cells.

That is why a tan is not produced as instantly as exposure to UV-A rays.

Due to its high energy, UV-B rays once absorbed into the skin do not deplete quickly, but retained for a long time.

UV-B accumulates to cause a slow 'tan' which results in delayed pigmentation of the skin(that is, those unsightly brown blocky patches).

Since both UV-A and UV-B are found in the sun's rays, exposure to the sun will cause the skin both to tan and to burn - the tan manifesting faster than the burn as explained above - appearing as if a tan always precedes a burn.

But one can obtain a tan without a burn(or less degree of burn) by the following methods:  

1. By exposure to a salon's sun-tanning bed(which emits only UV-A rays).

2. By applying a sunscreen that blocks out only the UV-B rays(that is preventing a burn caused by the UV-B rays but allowing the UV-A rays to penetrate the skin to cause the tan).

Some screens even contain active ingredients to speedify the tanning effect, by amplifying the UV-A rays penetration.

There are also suntan products which can amplify tanning - and within 10 to 15 minutes - under room lighting, without exposure to the sun.

Such products are often named as suntan lotions(milk, or the like).

Note that if one doesn't want to have a tan as well, then he/she should not apply a suntan lotion, but a broad spectrum sunscreen lotion instead(meaning a sunscreen with total block action - blocking UV-A and UV-B).

So do not get mixed up between suntan and sunscreen products.

Sunscreens are available in various strengths, measured in SPF terms.

SPF stands for Sun Protection Factor. 


The SPF of a sunscreen is determined by sampling a group of people by the following steps(usually not less than 25 people of various skin color tone):  

1.The human samples are made to expose their back to the sun.

Most parts of the body are covered, except the parts which are to be tested and measured.

Let's say there are 5 sunscreen products(named A, B, C, D, and E) of varying anti-UV strengths which need to be measured.

Then the person's back will have 6 holes, cut out from the shirt(or any covering) exposed to the sun.

One hole will have nothing applied on it.

The other five holes will each have one of the five sunscreens applied, and marked.

2. After every 5 or 10 minutes, the back of the human samples are examined to determine if a burn has occurred.

To elaborate, let's say after examining one of the human samples, the unprotected part was found to blister in 10 minutes, while the other 5 parts(on the back of the same person) each took 100, 150, 180, 200 and 220 minutes respectively to form the first sign of blisters.

The SPF is then computed by dividing each of these 5 values by 10 minutes(when it was unprotected).

Thus, the SPF value for the 5 sunscreens will be: Sunscreen A = 100/10 = SPF 10 " B = 150/10 = SPF 15 " C = 180/10 = SPF 18 " D = 200/10 = SPF 20 " E = 220/10 = SPF 22 It can be comprehended clearly that SPF is therefore a measure of the number of times a sunscreen will be able to protect a person before blister occurs as compared to his/her exposure to the sun if unprotected.

3. The readings of all the human samples are noted, averaged and compiled, to provide the SPF values for the respective sunscreens measured.

Since SPF is a measure of the number of times(and not absolute hours or minutes), and since such measurement is conducted on sampling of a small group of people, and taking their mean value(averages), note that a darker complexioned person may apply, say, an SPF 10 sunscreen and yet is better and more effectively protected than one who is fairer-skinned and wearing an SPF18 sunscreen.

Why so? Well, if the darker complexioned person were to take 30 minutes to blister under unprotected exposure, then applying an SPF 10 sunscreen will enable him/her to expose for 300 minutes before blistering occurs.

On the other hand, the fair-skinned person may get blisters after only 10 minutes of unprotected exposure.

So, an SPF 18 sunscreen will only protect him/her for 180 minutes.

Moreover, every person is different constitutionally.

A person's skin, although applying the same sunscreen, may not react exactly in the same manner as that which was determined from the small group of human samples.

Yet another factor.

The sampling that was conducted in a cold 4-seasonal climate(even if done during summer time with lots of sunlight) may not apply well to people living in the tropical and sub-tropical climates.

Therefore, one may find an SPF sunscreen good for protecting him/her up to, say, 200 minutes of exposure in a colder country, but realized that the same sunscreen could not last longer than 100 minutes at one of the beaches in Singapore, Malaysia, or Australia.

Different times of the year within one country will also have different amount of UV-A and UV-B rays, and as such, a sunscreen's protection time will vary according to the time of the year.

UV-rays are also absorbed and retained in swimming pools and in sea-water for some time even after the sun has set.

Therefore, swimming immediately after sunset may not be all that safe as most people presumed.

I would recommend early morning swim instead.

Staying at home or carrying an umbrella does not mean that one is not exposed to any UV rays absolutely.

The ground, the walls, the glass, the surroundings, all reflect light and UV-rays.

So long we are able to see any object(that is, objects are visible to our eyes), there are UV rays present, though in different degree depending on the time of the day and year.

This is so because we can see only when there's visible ray, and visible ray is just next to the UV-ray spectrum.

Therefore, whenever there are visible rays, there are UV-rays.

Moreover, higher SPF sunscreen doesn't necessarily mean better and more effective(especially those containing inorganic substances).

Higher SPF requires higher concentration of UV absorbers in the sunscreen, and thus a higher risk of developing skin reaction and allergy.

Sunscreens using organic substances such as TiO2(Titanium Dioxide) is safer, not only in that it is organic and less susceptible to allergy, but it also works by deflecting the UV-rays, rather than absorbing them and retaining on the skin's surface as in cases of inorganic UV absorbing agents.

I believe such retention of UV-rays on the skin's surface(especially those with higher SPF) will in the long run promote skin complications too.

However, unfortunately, organic substances alone do not seem to work more effectively than the synergistic effect of skillfully combining both organic and inorganic substances.

I hope the above explanation will help you and others in buying sun care products and in the choice of their relative SPF values more intelligently and more rationally.

Best Regards: Pierre