Possible Causes for Photosensitivity

Written by: SphynxCatVP
Link to original: http://sphynxcatvp.nocturna.org/health/day-photocauses.html

Photosensitivity can happen for many reasons, not just because of vampiric tendencies. Please take the time to rule out the mundane causes - wouldn't you feel better knowing that you have a medical condition that can be treated and being able to get it treated before it was too late? This article is broken down into the following sections:

(If you're looking for tips on how to deal with photosensitivity, that's covered here.)

The degree of photosensitivity varies among individuals. Not everyone who uses an item containing photoreactive agents will have a photoreaction. In fact, a person who has a photoreaction after a single exposure to a photoreactive agent may not react to the same agent after repeated exposures. OTOH, people who are allergic to one chemical may develop photosensitivity to another related chemical to which they would normally not be photosensitive. In such a case, a photosensitive reaction to one chemical increases a person's chance for a reaction to a second.

Although those with fair skin are more susceptible to photosensitizing, it is not uncommon for dark-skinned individuals to have chronic photodermatitis (light-related skin problems). Before going out into the sun, it's a good idea to check with your doctor to see if any of the medications you're taking is likely to cause problems and decide how to best avoid such reactions. Read the labels of OTC drugs and note if they are likely to be photosensitizing - the label may not specify that it is photosensitizing, but if you're familiar with what's on the chemical list, it'll be easier to weed them out. If you get symptoms after being out in the sun, you may want to consider what drugs and chemicals you are using and contact your doctor or other medical professional immediately about advice.

UV wavelengths

Did you know ultraviolet rays are classified into three different wavelength sizes? (Maybe more, but I've only heard about three.) They run approximately like this:

  • UV-C: 200 - 280 nanometers (Commonly given off by welding equipment)
  • UV-B: 290 - 315 nanometers
  • UV-A: 340 - 400 nanometers (UV-A I, or "Far" UV-A)
  • UV-A: 315 - 340 nanometers (UV-A II, or "Near" UV-A)

The UV-A / UV-B wavelengths are commonly referred to on packages of sunscreen lotion (and now you know the wavelengths!) but UV-C is a factor as well - especially with exposure to sunlight and full-spectrum light sources - even if it's not as commonly known. UV-C is also given off by various types of welding equipment. Those of you who may be welding for a living, or know someone who is, will need to take this into account.

Types of photosensitive reactions


Chemicals that produce a photoreaction (reaction with exposure to UV light) are called photoreactive agents, or more commonly, photosensitizers. After exposure to UV radiation either from natural sunlight or an artificial source such as tanning booths or bug zappers, these photosensitizers cause chemical changes that increase a person's sensitivity to light, causing the person to become photosensitized. Photoreactive agents can cause both acute and chronic effects, which include the following (this is not an exhaustive list):

  • Acute effects:
    • Exaggerated sunburn-like conditions, eye burn, mild allergic reactions, hives, abnormal reddening of the skin, and eczema-like rashes with itching, swelling, blistering, oozing and scaling of the skin.
  • Chronic effects:
    • Premature skin aging, stronger allergic reactions, cataracts, blood vessel damage, a weakened immune system, and skin cancer.

Photosensitizers can cause either photoallergic or phototoxic reactions. Because drug-induced photosensitivity disorder symptoms mimic sunburns, rashes and allergic reactions, many cases go unreported. Also, although research has shown that the numbers of photosensitized individuals may be high, most people do not associate the sun's light with the development of their skin eruptions.

Photoreactive products can also aggravate existing skin problems like eczema, herpes, psoriasis and acne, and can inflame scar tissue. They can also precipitate or worsen autoimmune diseases, such as lupus erythematosus and rheumatoid arthritis, in which the body's immune system mistakenly destroys itself.


This type of reaction appears as a rash or reddened area of skin, sometimes with blistering or swelling. It is caused by a change in one's immune system (which can be due to any one of many different factors), and the symptoms appear every time the skin is exposed to sunlight. In photoallergic reactions, which generally occur due to medications applied to the skin, UV light may structurally change the drug (a light-induced chemical reaction) causing the skin to produce antibodies. The result is an allergic reaction. (An example of this type of allergic reaction would be a reaction to poison ivy, although the poison ivy problem is not light based.) Symptoms can appear within 20 seconds after sun exposure, but can also be delayed - one photoallergic reaction documented in a medical magazine on Contact Dermatitis took three months to develop. (That was a reaction to a topical NSAID - Non Steroidal Anti Inflammatory Drug - called Suprofen, not approved for use in the USA.) /p>


Phototoxic reactions, which do not affect the body's immune system, are more common than photoallergic reactions. These reactions can occur in response to injected, oral or topically applied medications. Phototoxic reactions look and feel like an extreme sunburn. They are usually the result of a reaction between a certain chemical (medicines, shampoos, etc.) and sunlight.

In a phototoxic reaction, the drug(s) absorb the energy from UV light and releases the energy into the skin, causing skin cell damage or death. The reason occurs from within a few minutes to several hours after UV light exposure. Though sunburn-like symptoms appear only on the parts of the body exposed to UV radiation, resulting skin damage can persist, with or without continuing exposure to UV rays. In some cases, people exposed to photoallergens may continue to have phototoxic skin eruptions up to 20 years after discontinuing use of the offending product, even though they avoided further exposure to the photoallergens. Yeouch!

Because drug induced photosensitivity disorder symptoms mimic sunburns, rashes and allergic reactions, many cases go unreported. Also, although research has shown that the numbers of photosensitized individuals may be high, most people do not associate the sun's light with the development of their skin eruptions.


This is a a condition of abnormal sensitivity to light (i.e., the amount of light entering the eye); usually, the iris is unable to constrict enough to reduce the light entering the eye to a comfortable level. . This condition is normally a symptom of associated disorders or disease (e.g., corneal inflammation, aphakia, iritis, or ocular albinism). Some drugs and/or poisons also can cause photophobia by causing pupil dilation (notably, amphetamines and antihistamines, cannabis and cocaine, atropine, scopolamine, mydriotics and cycloplegics (these are drugs used to dilate the pupils during an eye exam - Mydriatics only dilate the pupils; cycloplegics dilate the pupils and paralyze the muscles used in accommodation - photophobia is a temporary condition following the use of these drugs and lasts until the drug wears off, usually several hours) and strychnine). Sometimes glasses with anti-reflective coatings will help - but not always! I tried anti-reflective coatings on a pair of new glasses, and it only made the problem worse. Anti-reflective coatings (at least from this particular company) reduce the glare seen on your lens, that's all. If your photophobia is triggered by glare, then it may help. If your photophobia is due to purely the amount of light, then it will only make the problem worse because it reduces the glare by allowing more light through the lens.

Photophobia can be the body's way of attempting to let the eye heal after a recent injury, as well, see "Corneal Abrasion" in the physical conditions section.

FWIW, I don't particularly agree with "photoPHOBIA" as an accurate term - just because something hurts doesn't necessarily mean a person is afraid of it. But I don't expect the medical community to change this just because some "weird person" comes up with a reason not to use it. *laughs*

The role of genetics and environment

And no, I don't mean "vampire genes". :)

Certain people are genetically predisposed towards photosensitivity in varying degrees, such as if you have pale skin and/or light colored eyes. Someone who's Swedish, for instance, will *tend to* be much more sensitive than someone who's from the Mediterranean. If you work shifts that don't expose you to a lot of sunlight (such as working night shift as a security guard) you may be more sensitive just because you haven't been out in the sun as much. Pale skinned people ARE much more prone to sunburn - thus, a higher SPF sunscreen is usually recommended for them as a result. Not much can be done about this, except to protect your skin and eyes.

If you always wear sunglasses when you go out during the day, your eyes will become more sensitive because they're not exposed to as much light. As long as the sunglasses block 100% of UV rays, this is not necessarily a bad thing!

Some cases of glaucoma or cataracts have been linked to excessive exposure to UV rays, particularly from the sun or in tanning booths. (Hence why I say wearing sunglasses all day isn't necessarily a bad thing. *grins*) It just means you need to keep wearing the sunglasses (which medical folks are now strongly hinting that you should be wearing anyway) or if you're bound and determined to fry your eyes :) just force yourself to get used to the bright shiny yellow thing in the sky again.

Example medications that can cause photosensitive reactions

Azulfidine sulfasalazine antiarthritic, antibiotic.
Bactrim trimethoprim antibiotic
Cordarone Amiodarone antyarrhythmic
Crystodign digitoxin antiarrhythmic (heart medication)
Diabinese chlorpropamide antidiabetic (oral)
Doxycycline Doxycycline Tetracycline class antibiotic
Duraquin quinidine antiarrhythmic
Feldane piroxicam NSAID, antiarthritic
Motrin Ibuprofin NSAID, antiarthritic
Orinase tolbutamide antidiabetic
Phenergan promethazine antihistamine
Tolinase tolazamide antidiabetic
Sinequan doxepin antidepressant
Vibramycin doxycycline antibiotic

This is by no means an exhaustive list - and you can find other lists of photosensitizer drugs here:

Some common items that may cause photosensitivity in some people

  • Sunscreens containing: PABA, bergamot oil, sandalwood oil, benzophenones, cinnamates, salicylates, anthranilates, PSBA, mexenone and oxybenzone. (Some information on various sunscreen chemicals is here or you can see my article on sunscreens.)
  • deodorants
  • antibacterial soaps
  • artificial sweeteners
  • fluorescent brightening agents for cellulose, nylon and wool fibers
  • napthalene (mothballs)
  • petroleum products (such as petroleum jelly, "Vaseline" being an example)
  • cadmium sulfide (a chemical injected into the skin during tattooing)
  • Vitamin deficiency

Diseases, genetic disorders and other physical conditions with photosensitivity

These links are courtesy of the E-Medicine website, and will have some medical terminology. This is not a complete list, this is only a jumpoff point.

Tanning booths

Tanning booths and the use of indoor tanning products (sometimes called the "tan in a bottle" method) can be more of a problem than natural sunlight, and this is true with photosensitivity reactions as well as in general. FDA enforces policies in which sunlamp product manufacturers much develop an exposure schedule and establish a minimum recommended exposure time (and therefore the maximum time interval) based on the characteristics of their particular products. This information must appear on the products label and in no way is to be considered as a safe limit.

The FDA warns that some tanning operators may claim that UV-A sunlamps are safer than the sun and UV-B lamps. This is not true. In fact, exposure to the UV radiation from sunlamps adds to the total amont of UV radiation you get from the sun during your lifetime, further increasing your risk for cancer, and increasing the amount of visual aging you have later on (i.e., wrinkles, thickened "alligator feel" skin, spots, etc.)