Answer to Reader question concerning sunscreen Riemann P20

After my post on the skin and the sun, “Cookie Monster” asked:

“Hi! When i go running i use a sunscreen called ‘Riemann P20′. Its great because all you do is shake it before use, its almost like a liquid/oil/fluid of some sort, and dries quickly and i don’t seem to ‘sweat it off’. Is this a product you would recommend? A friend of mine mine swears by P20 and tells me her children have never been sunburned, but only if they wait about half an hour or an hour before they go out in the sun. She claims they only need to put it on once a day (so she won’t have to obsess about using sun screen on her kids every 30 min at the beach). What is your opinion about this? Only negative thing about this sunscreen is that it doesn’t smell too good. It smells a little gasoline-like or like nail polish remover. Can that be good for the skin?”

First of all "Cookie Monster", thank you so much for bringing up this concern! I hadn’t heard of this sunscreen before you asked me about it, and now I’m very happy you did. It was quite an educational adventure doing this assessment.

The active ingredient of Riemann P20 is called PABA (Para-aminobenzoic acid).  It occurs naturally in the body as a B complex vitamin otherwise know as vitamin Bx. It can also be found in eggs, meat and cereals and it is minimally toxic.

In sunscreens PABA acts as a dye that absorbs UVB light energy and converts it into heat as a function of its benzene ring (hence the gasoline smell ;) It does this with 95% efficacy according to the manufacturer, given that you apply the sunscreen a whole 90 minutes prior to sun exposure (jeez, that’s a long time!).

I’ve summarized my findings of Riemann P20 into ‘yay’ and ‘nay’ categories for simplicity.


  1. Protects against UVB rays with high efficacy.
  2. PABA’s have been used to reduce skin lesions associated with dermatitis (eczema)
  3. Have been used in mending skin discoloration in Vitiligo (disease in which person lacks skin pigment)


  1. It protects against UVB radiation ONLY! This stops you from burning, while letting you tan, but the cumulative effect of unhindered UVA radiation can be severely damaging as it has been shown to not only be responsible in large part for the aging process of photo aging, but its role in skin cancer development is also becoming more and more evident.
  2. Also, only effective if applied 90 minutes before exposure. Outrageous! Who has time to wait 90 minutes from application before leaving the house? Or is it only me that end up with 15 min to go before I have to be somewhere? (don’t answer that if yes)
  3. According to ‘Clinical Dermatology’ PABA can lead to skin abnormalities including discoloration to cancer (gasp!)
  4. PABA contributes to the release of oxygenated free radicals, which are linked, to increased skin pigmentation and aging.
  5. Like all chemicals, PABA might induce allergic reactions. According to a recent article PABA was recognized as both a topical (effect from applying it on skin) photo sensitizer but also a systemic  (when ingested, inhaled etc) one. Topically applied, PABA was introduced as one of the first chemical sunscreen agents in the 1920s, gaining wide usage after World War II. In the course of time, however, PABA became one of the most common causative substances of photo allergic contact dermatitis (sun induced skin allergy) due to sunscreens. Increasing awareness of its photo sensitization properties led to a switch to PABA-free sunscreens during the eighties after a 1989 FDA report stated that PABA esters damage DNA, thus increasing risk of skin cancer.
  6. Alcohol Denat is one of the ingredients and is a known irritant.
  7. Also contains Hydroxypropyl Cellulose , a comedogenig agent (meaning it can block your pores and give you pimples)

Phew! That was a mighty long nay list!

To answer your question plainly dearest "Cookie Monster", I wouldn’t recommend Riemann P20 based on the evidence I found researching it, there are other sunscreens on the market containing both UVB and UVA protective agents that are fast absorbing and sweat proof for your running sessions.

My recommendation for your runs is the La Roche Posay ANTHELIOS XL SPF 50+ FLUIDE EXTREME For Face (this sunscreen has been voted the best in the world!) I haven't tried it myself yet as I like to stick to physical sunscreens more, but I have a friend who loves this.

If you would like to continue using your Riemann P20 I recommend you to use another sunscreen on top, perhaps one with a physical filter so to ensure your not getting any of those aging UVA rays while your keeping the rest of your body in shape.

My favorite at the moment is Skinceuticals Physical Fusion UV Defense SPF 50

But as this is at Mr.ROK's appartment in London I wasn't able to include it in my current suncare products post.

I hope you got an answer you’re happy with dearest ROKer! Even if it means thinking of switching sunscreen.



 The Mechanisms of UV Mutagenesis

Hironobu IKEHATA* and Tetsuya ONO

J. Radiat. Res., 52, 115–125 (2011)

Invited Review

Uro-dermatological problems of a construction worker: paraaminobenzoic acid as a systemic photosensitizer

European Journal of Dermatology. Volume 20, Number 2, 217-9, March-April 2010, Clinical report DOI : 10.1684/ejd.2010.0876 Author(s) : Johanna Stoevesandt, Natalie Kürzinger, Eva Bettina Bröcker, Axel Trautmann , Department of Dermatology, Venereology and Allergology, University of Würzburg, Josef-Schneider-Straße 2, D - 97080 Würzburg, Germany.

Morphological and Biochemical Changes During Aging and Photoaging of the Skin of C57BL/6J Mice

2010 The Japanese Society of Toxicologic Pathology - Ayako Sayama, 1 Tomomi Soushin, 1 Taro Okada, 1 Kunio Doi, 1 and Hiroyuki Nakayama 1

Effect of UVA irradiation on proliferation and NO/iNOS system of human skin firbroblast

CHEN Minglian, ZHANG Buiying, YI Mei, CHEN Xiao, LI Ji, XIE Hongfu, CHEN Xiang

J Cent South Univ (Med Sci) 2009, 34 (8)

“Orlando Sentinel” Cancer experts fear report will cause sunscreen scare;

Alex Beasly; March 1989