Photosensitivity

Nearly everyone will burn if exposed to enough ultraviolet radiation from the sun or other sources. However, some people burn particularly easily or develop exaggerated skin reactions to sunlight. Doctors call this condition photosensitivity. For some people, taking certain medications or plant products—or rubbing them on their skin—can cause photosensitivity. Similar reactions are seen in diseases such as some forms of porphyria (a group of usually hereditary metabolic disorders) or lupus. In another condition, called polymorphous light eruptions, dramatic rashes can develop after fairly limited sun exposure.

The most important step toward treating photosensitivity is to identify whether an external substance is causing the reaction, and then eliminate it if possible. Antibiotics are among the most common photosensitizing drugs. Many other natural substances can also cause this reaction. Another commonsense step is to use sunscreen and wear protective clothing, or simply to stay out of the sun.

Some types of photosensitivity may respond to specific treatments such as oral beta-carotene, steroids, or other medications.

Principal Proposed Treatments for Photosensitivity:

As with conventional treatment, natural treatment begins with identifying any potential photosensitizing substances, including herbs. Beta-carotene may be helpful for treating polymorphous light eruptions or the photosensitivity of porphyria.

St. Johns Wort and Other Plants: Can Cause Photosensitivity

A number of common herbs and plant products are known to provoke extreme reactions to sunlight in some individuals. One of the more well-known culprits is St. Johns wort, which has caused fatal photosensitivity reactions in cattle that grazed on it. However, in one study of highly sun-sensitive people, double doses of the herb produced mild increases in reaction to ultraviolet radiation. There is also one report of a severe skin reaction in an individual who used St. Johns wort and then received ultraviolet therapy for psoriasis. In addition, topical St. Johns wort apparently caused severe sunburn in one individual. For this reason, photosensitive individuals should probably avoid St. Johns wort.

Photosensitivity can also result from touching or eating other plants, including celery, dill, fennel, fig, lime, parsley, and parsnip, as well as arnica, artichoke, chrysanthemum, dandelion, lettuce, endive, marigold, and sunflower. Lest you swear off gardening or salads altogether, be aware that most people do not react to these plants. Essential oils—of lime, for example—may be more problematic than the plant itself.

Beta-Carotene: May Help, but Evidence Is Conflicting

Beta-carotene, a plant pigment giving color to carrots and yams, may be beneficial for at least two kinds of photosensitivity: polymorphous light eruptions and photosensitivity caused by certain types of porphyria. It is the best-studied supplement for photosensitivity, although only four studies on it have been placebo-controlled and these had conflicting results. According to one theory, beta-carotene prevents skin damage by neutralizing free radicals, harmful chemicals created in the skin by the action of radiation.

One characteristic of beta-carotene is that it gives a deep yellow color to human skin when taken in high doses for several months. Since supplementation must go on for a while to see results, this side effect makes it difficult to conduct a truly double-blind study in which neither researchers nor the participants know who is taking the active compound and who is taking placebo. Once people begin to turn yellow, they are likely to figure out what theyre taking, possibly affecting the study outcome. Therefore, even the results of placebo-controlled studies of beta-carotene are open to question.

What Is the Scientific Evidence for Beta-Carotene?

Three controlled trials of beta-carotene for polymorphous light eruptions (PLE) found mixed results. A 10-week study in 50 people with PLE given beta-carotene plus canthaxanthin (another carotene) or placebo found evidence of significant benefit. However, in two other controlled trials of beta-carotene alone, lasting 12 to 15 weeks (the number of participants was not reported), modest benefits were seen in one study and no benefits at all in the other. None of these studies were truly double-blind (for the reason mentioned above).

Many uncontrolled studies have reported that beta-carotene extends the time that people with erythropoietic protoporphyria (EPP) can safely spend in the sun. However, an 11-month controlled trial found no benefit. A few case reports suggest beta-carotene may also be helpful in another kind of porphyria called porphyria cutanea tarda. However, such studies cannot rule out the power of suggestion.

Several studies have found beta-carotene to be helpful in preventing ordinary sunburn, but, again, other studies found no benefit.

For more information, including dosage and safety issues, see the full beta-carotene article.

Other Proposed Treatments for Photosensitivity:

Other treatments sometimes recommended for preventing the photosensitivity of porphyria include vitamins C and E, EGCG (a bioflavonoid found in green tea), adenosine monophosphate (AMP), and vitamin B6. However, evidence for the effectiveness of these treatments is fairly minimal.

One gram daily of vitamin C was given to 12 people with EPP in a double-blind placebo-controlled trial. Although 8 of the 12 reported improved sunlight tolerance, the study was too small for the results to be statistically significant.

In an uncontrolled study of AMP in 21 people with porphyria cutanea tarda, many showed decreased photosensitivity, much to the surprise of the investigator. Two cases of EPP were also reportedly improved by vitamin B6. In addition, nicotinamide—another B vitamin—was found to help prevent polymorphous light eruptions in an uncontrolled study of 42 people.

Evidence that vitamin C and vitamin E may help prevent sunburn in people without photosensitivity provides indirect evidence that these substances may be helpful for photosensitivity as well. However, a small double-blind placebo-controlled trial of individuals with polymorphous light eruption found no benefit with combined vitamin C (3 g per day) and vitamin E (1,500 IU per day).

Studies on laboratory animals found that topical vitamin C and vitamin E, alone or together, helped prevent burning on exposure to ultraviolet light. Two placebo-controlled human studies, one only partially blinded, found that a combination of oral vitamin C and E also modestly reduced skin redness from UV radiation. However, placebo-controlled human studies of oral vitamin E or C taken alone found that they didnt help.

Theoretically, EGCG may also reduce photosensitivity. Research suggests that spreading it on the skin may help prevent sunburn caused by ultraviolet rays in both animals and people.