Understanding PABA Allergies and PABA-free Sunscreen Options

According to the American Cancer Society, "more than 1 million skin cancers are expected to be diagnosed in the United States in 2009". The use of sunscreen and the protection of exposed skin could prevent most of these skin cancers. (1) If you enjoy the outdoors, your nearby bottle of sunscreen may be the most convenient form of sun protection. Before you reach for that sunscreen next time, ask yourself a quick question. How much do you really understand about sunscreen and your sunscreen options?

The active ingredients are what give sunscreens their protective properties. These ingredients can be organic, inorganic, and sunscreens usually contain a mixture of both. The ingredients work by either reflecting ultraviolet (UV) radiation or absorbing UV radiation and dispersing it as heat. (3)

There are two types of UV radiation that are responsible for sunburns and skin damage. Long wavelength UV-A rays which penetrate deeply into the skin's dermis layer and UV-B rays which are responsible for most sunburns. Both UV rays however can contribute to the formation of skin cancer. Having a sunscreen that can block both these UV rays would then ideally provide the most protection. (2,3)

One of the earliest active ingredients used in sunscreen was para-Aminobenzoic Acid (PABA). While PABA is a powerful UVB absorber, it does not absorb UVA rays. PABA can also attach to skin proteins so it is not easily washed off while swimming. (5) Since PABA needs to be mixed with alcohol for application formulas, it can sting when applied to skin. PABA can also stain clothing. What has led most sunscreen manufacturers to abandon its usage were allergic reactions, dermatitis, or perceived sensitivity to PABA and its ester derivatives. (6)

Sunscreen manufacturers today use a combination of active ingredients in their PABA-free sunscreens. They typically contain a mixture of broad-spectrum UVA and UVB absorbers to provide the most protection. While they are often advertised as hypoallergenic since they are PABA-free, this can be misleading as other components of sunscreen and alternate UV absorbers can still produce an allergic reaction in individuals. Individual immune systems determine what is an allergen and how their body responds to a perceived attack. What may be harmless to one person may cause the formation of antibodies in another. (6,7)

The active ingredients in sunscreens found in the United States typically contain one or more of the following classes of compounds - Benzophenones, Cinnamates, Salicylates, Dibenzoylmethanes, Anthranilates, Methylbenzylidene Camphor, Octyl Triazone, 2-Phenylbenzimidazole-5-Sulfonic Acid, and Octocrylene. Only Anthranilates do not have any reported cases of allergic reactions. The other classes have a range of documented responses from rare to infrequent. (6)

UVB Absorbers:
Benzophenones - while primarily UVB absorbers, some esters are UVA absorbers. It is marketed under a variety of names. It is a common cause of photocontact allergy.

Cinnamates - They are primarily UVB absorbers and are often mixed with benzophenones. They mix poorly with water and often give sunscreens their 'waterproof' characteristic. Cinnamates infrequently produce an allergic reaction.

Salicylates - They are weak UVB absorbers and are often used to help solubilize other UV absorbers. They appear to rarely cause an allergic response.

Methylbenzylidene Camphor - It is a UVB absorber and has produced a few documented cases of an allergic reaction.

Octyl Triazone - It is a UVB absorber and there is only one documented case of an allergic reaction.

Octocrylene - This is UVB absorber. It is relatively new as a sunscreen agent and has produced only two documented cases of an allergic reaction.

UVA Absorbers:
Dibenzoylmethanes - They have a wide absorption spectrum but are mainly UVA absorbers. While most esters in this class rarely produce a reaction, one was removed from the market in 1993.

Anthranilates - They are UVA absorbers and there are no documented cases of allergic reactions.

2-Phenylbenzimidazole-5-Sulfonic Acid - It is a UVA absorber and only has a few documented cases of an allergic reaction.

Alternative compounds that do not have any documented cases of allergic responses are, drometrizole trisiloxane, bisethylhexyloxyphenol methoxyphenol triazine, drometrizole, dioctyl butamido triazone, and terephthalylidene dicamphor sulfonic acid. Compounds that can be found in sunscreens and physically block UV rays rather than absorb are titanium dioxide and zinc oxide. They do not appear to cause dermatitis or photoallergy. (6)

To get the most out of a sunscreen, shake it well to mix the ingredients. Reapply it as you exercise. Throw out any expired sunscreen. Active ingredients can have a limited shelf life. In the absence of an expiration date, the FDA requires sunscreens to be stable at their labeled strength for three years. Storage temperatures can degrade the active ingredients in sunscreens. When in doubt, throw it out. (2,4)

There are a number of active ingredients found in sunscreens today. Find a sunscreen that contains ingredients that you aren't allergic to and provides a broad spectrum of UV protection. Don't judge a sunscreen by its price, the less expensive one may well provide more protection. Look for the SPF label and buy one with a minimum of SPF 15. One with waterproof properties will help keep you protected when participating in watersports.

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Sources:
1. American Cancer Society. 2009 Cancer Facts and Figures. http://www.cancer.org/downloads/STT/500809web.pdf

2. http://www.aad.org/media/background/factsheets/fact_sunscreen.htm

3. http://www.loc.gov/rr/scitech/mysteries/sunscreen.html

4. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5104a3.htm

5. Helms, Richared, et. al, "Textbook of Therapeutics", Eighth Edition

6. http://www.medscape.com/viewarticle/528577_7

7. http://www.webmd.com/allergies/living-with-8/chronic-allergies-causes