What is Photo-dermatitis?
Photo-dermatitis is a type of allergic contact dermatitis triggered by UV light (artificial or natural sunlight), sensitising the allergic reaction and causing a rash. It is mostly triggered by the use of sunscreen or by taking certain drugs. Second and subsequent exposures produce photoallergic skin conditions which are often eczematous. Photo-dermatitis is also often known as “Sun-poisoning” or “Photo-allergy”.
Fragrances (particularly lemon oil or musk ), topical non-steroidal anti-inflammatory drugs such as Ibuprofen, and some antibacterial soaps or creams containing hexachlorophene can all cause this type of dermatitis when they’re exposed to sunlight.
Contact dermatitis to sunscreens is fairly common and often occurs because of an allergy to the fragrances and preservatives in the product. However the most common photo-allergens or triggers for photo-dermatitis are the chemicals used as a UV filter in the manufacture of sunscreens, which are of course worn constantly when you’re in the sun! So basically this type of photo-dermatitis is actually Sunscreen Allergy.
It can occur anywhere on the body where the sunscreen has been applied, although it tends to be more common on those areas with the most exposure to the sun. This is called "photo-contact dermatitis," and shows in a sun-exposed pattern on the face (but not the eyelids or the area of the neck under the chin), the backs of the hands and the forearms and the "V" area of the upper chest and lower neck.
Who is at risk from Sunscreen Allergy?
Those most a risk for developing sunscreen allergy include the following:
- Females, possibly as a result of higher use of cosmetics containing sunscreens
- People with chronic sun-related skin conditions, such as sun-damaged skin
- People with atopic dermatitis
- People who have applied sunscreens to damaged skin
- People with outdoor occupations
Which Chemicals in Sunscreens Cause Allergies?
Many active ingredients in sunscreens cause contact dermatitis and as many sunscreens have multiple active ingredients it may be difficult to determine the exact cause without patch testing for the individual chemicals.
The following are the most common active ingredients in sunscreens reported to cause contact dermatitis:
Para-Aminobenzoic Acid (PABA). PABA was one of the earliest chemicals used in sunscreens, but is now rarely used due to its many side effects including contact dermatitis. It also tends to stain clothing.
Many sunscreens are falsely labelled “hypoallergenic” since they do not contain PABA, but can still cause contact dermatitis from other active ingredients.
A number of chemicals related to PABA are still used today, including padimate A and O so people allergic to PABA may also be allergic to these or other similar chemicals, including para-phenylenediamine (found in hair dye) and sulfonamide (sulfa) medications.
Benzophenones. These have been used in sunscreens for 50 years, and are one of the most common causes of sunscreen-induced contact dermatitis. Watch for other names for benzophenones on sunscreen labels including oxybenzone, Eusolex 4360, methanone, Uvinal M40, and diphenylketone.
Salicylates. Benzyl salicylate was the earliest sunscreen used. Common chemicals in this group used today include octyl salicylate, homosalate and any chemical ending with “-salicylate.” Salicylates are rarely implicated in contact dermatitis so are considered safe.
Dibenzoylmethanes. These include the chemicals avobenzone and Eusolex 8020. They are frequently combined with other chemical absorbers in sunscreens.
Cinnamates. Cinnamates are less commonly found in sunscreens but are widely used as flavourings and fragrances in everything from toothpaste to perfumes. These chemicals are related to Balsam of Peru, cinnamon oils and cinnamic acid and aldehyde. People allergic to cinnamates may therefore also be allergic to these other chemicals. Other names of cinnamate containing chemicals include Parsol MCX and any chemical ending with “–cinnamate.”
Octocrylene. Octocrylene is a relatively new chemical used in sunscreens, but has been reported to cause contact dermatitis. It is similar to cinnamates, and may be used together with cinnamate chemicals in sunscreens
What Sunscreens Can be Used in People with Sunscreen Allergy?
Sunscreens work in one of two ways:
Chemical Absorbers: These sunscreens are rubbed into the skin and absorb ultraviolvet (UV) radiation from the rays of the sun, turning this energy into a less dangerous form of radiation that causes less damage to the skin.
Physical Blockers: These sunscreens reflect the sun’s radiation away from the skin, so that it is not absorbed.
Physical sun-blockers include zinc oxide and titanium dioxide and tend to come in heavier creams that sit on the surface of the skin as they do not absorb well. Zinc oxide, a mineral that provides complete UVB/UVA protection and has anti-inflammatory properties is a favourite with sportsplayers and the only FDA approved sunscreen for use on children under 6 months of age.
Physical sun-blockers have not been reported to cause contact dermatitis and are a good choice for people with allergy to sunscreens or those with the concern of developing an allergy to sunscreens.