Photosensitivity

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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.

 

 

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Principal Proposed Natural Treatments

Beta-carotene, a plant pigment giving color to carrots and yams, may be

beneficial for at least two kinds of photosensitivity: polymorphous light

eruptions6,7 and photosensitivity caused by certain types of porphyria.8–10 It

is the best-studied supplement for photosensitivity, although only four studies

on it have been placebo-controlled and these had conflicting results.11–13

According to one theory, beta-carotene prevents skin damage by neutralizing free

radicals, harmful chemicals created in the skin by the action of radiation.14

 

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.

(For reasons why double-blinding is so important, see Why Does the Natural

Pharmacist Rely on Double-blind Studies?) Once people begin to turn yellow, they

are likely to figure out what they're taking, possibly affecting the study

outcome. Therefore, even the results of placebo-controlled studies of

beta-carotene are open to question.

 

That said, 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.15 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.16

 

Many uncontrolled studies have reported that beta-carotene extends the time that

people with erythropoietic protoporphyria (EPP) can safely spend in the

sun.17–19 However, studies that lack a control group, as these did, are

notorious for producing over-optimistic results, and an 11-month controlled

trial found no benefit.20 A few case reports suggest beta-carotene may also be

helpful in another kind of porphyria called porphyria cutanea tarda.21

 

Several studies have found beta-carotene to be helpful in preventing ordinary

sunburn,22–25 but, again, other studies found no benefit.26,27

 

For more information, including dosage and safety issues, see the full

beta-carotene article.

 

Other Proposed Natural Treatments

Many, though not all, studies suggest that vitamin C and vitamin E (taken orally

or used topically) may help prevent sunburn in people without

photosensitivity.43–49,54

 

On this basis, these vitamins have been tried for photosensitivity as well. In a

double-blind, placebo-controlled trial of 12 people with EPP, one gram of

vitamin C taken orally daily appeared to help reduce symptoms.38 However, the

study was too small for the results to be statistically significant.

 

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).42

 

Some research suggests that topical application of ECGC (a component of green

tea) may also help prevent sunburn;51–53 effects on photosensitivity are

unclear.

 

In an uncontrolled study of AMP in 21 people with porphyria cutanea tarda, many

showed decreased photosensitivity, much to the surprise of the investigator.39

 

Two cases of EPP were also reportedly improved by vitamin B6.40 In addition,

nicotinamide—another B vitamin—was found to help prevent polymorphous light

eruptions in an uncontrolled study of 42 people.41

 

Herbs and Supplements to Use Only with Caution

St. John's 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. John's wort, which has caused fatal photosensitivity reactions in cattle

that grazed on it. In one study of highly sun-sensitive people, double doses of

the herb produced mild increases in reaction to ultraviolet radiation.1 There is

also one report of a severe skin reaction in an individual who used St. John's

wort and then received ultraviolet therapy for psoriasis.2 In addition, topical

St. John's wort apparently caused severe sunburn in one individual.3 For this

reason, photosensitive people should probably avoid St. John's 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.4,5 Lest you swear off gardening or salads altogether, be aware that

most people do not react to these plants. Essential oils of plants may be more

problematic than the whole plant itself.

 

Hope this helps

S