Extra Sunscreen Needed: Photosensitizing Ingredients

The summer months are upon us. Just like some medications, certain supplements can increase sun sensitivity. This is a good time to remind patients to use extra sun protection – particularly if they use alpha hydroxy acids (AHAs), bergamot, or St. John’s wort.

AHAs are a group of natural acids found in foods, including citric acid, glycolic acid, lactic acid, malic acid, and tartaric acid. They’re commonly used in topical anti-aging products, with glycolic acid having the strongest evidence of benefit – applying glycolic acid to the skin seems to reduce wrinkles and other signs of aging. But like all AHAs, it can also increase the risk of getting a sunburn. Tell patients to use extra sunscreen and protective clothing if they use any products containing AHAs.

Also remind patients who take St. John’s wort that it is a very strong photosensitizer. Both oral and topical use can lead to sun poisoning. It contains the chemical hypericin, which seems to be responsible for these effects. Taking 1.8-4 grams St. John's wort extract or 5-10 mg hypericin daily seems to be the average dose range leading to increased sun sensitivity.

Bergamot oil is also one to watch out for. It’s often used in essential oil products, but when applied to the skin it can increase sun sensitivity. It contains a chemical called psoralen, which makes the skin more sensitive to ultraviolet (UV) light. Psoralens are found in some drugs used for psoriasis phototherapy treatment. Tell patients not to use bergamot oil on the skin.

Many other natural medicines also have photosensitizing effects. Refer to our photosensitizers monograph class to learn more.