Photosensitivity is an abnormal skin response involving the interaction between
photosensitizing substances and sunlight or filtered or artificial light at wavelengths
of 280-400 nm. There are two main types: photoallergy & phototoxicity.
How does it present?
The abnormal skin response can be the development of a skin rash, an exacerbation
of an existing rash, an exaggerated sunburn or symptoms such as pruritus (itchy
skin) or paraesthesia (burning) after exposure to the light.
Photosensitivity is common and probably affects members of all racial and ethnic
groups, although there has been no studies of its prevalence in the general population.
Drugs likely to cause Photosensitivity
Tricyclics: Elavil, Asendin, Tofranil, Surmontil
Cetirizine (Zyrtec, Razene)
Loratidine (Claratyne, Lora-tab)
ACE-inhibitor: Captopril, Accupril, Univasc
Beta- Blockers: Sotalol
Calcium Chanel Blockers: Diltiazem, Nifedipine
Lipid Lowering: Simvastatin (Zocor)
Coal Tar & derivatives
Quinolones: Cipoxin, Norfloxacin (Noroxin),
Sulfonamide: Bactrim, Septrim
Tetracyclines: Minocycline (Minocin, minotab), Vibramycin
Phenothiazines: Phenergan, Stelazine, Thorazine
Thiazides: bendrofluazide (Neonaclex), chlorothiazide
St Johns Wort (hypericum)
Non-Steroidal Anti-inflammatory Drugs (NSAIDs)
Oestrogens & Progesterones
Perfume oils: Bergamot, citron, Lavender, Sandalwood, cedar, Musk
Dioxbenzone (Eclipse, PreSun, Shade)
Vitamin A Derivatives
Benzyl Peroxide (Anti-acne)
Prevention of Drug Photosensitization
Patients taking medication that are likely to cause photosensitivity should minimise
exposure to sunlight & use broad-spectrum sunscreens & protective clothing.
Once daily medication should be taken in the evening.
Chronic photosensitivity appears to be much less common than acute photosensitivity.
The prevalence is uncertain, as it is probably under-diagnosed, because patients
are often unaware that a skin eruption is caused by sunlight.
The eruption is usually present year-round, but sometimes it is present only in
warm months. Exposure to sunlight could exacerbate the eruption or may produce little
change. The key point to the diagnosis is that the rash is mainly confined to exposed
Types of Chronic Photosensitivity
Chronic Actinic Dermatitis is rare. It mainly affects men over
the age of 60 yrs.
It presents with eczema on exposed areas year-round or mainly in
It is treated with Sun avoidance or desensitization with phototherapy
or immune suppressive drugs.
Actinic Prurigo is rare and affects the sexes equally. It affects
It presents with intensely itchy papules (bumps) & nodules
(larger bumps), often with inflamed lips & scarring.
It is treated with sun avoidance & desensitisation with phototherapy
Photoexacerbated atopic eczema mainly affects females at any age.
It presents with eczema on exposed areas. There is usually a history
of flexural eczema and possibly Hay fever and asthma.
It is treated with sun avoidance & desensitization with phototherapy.
Porphyra cutanea tarda is a rare form of photosensitivity affecting
mainly adult males.
It presents with erosions (sores) & bullae (blisters) after
minor trauma, mainly on the backs of the hands & forearms.
It is diagnosed by measuring urinary porphyrins & treated
by venesection & chloroquine.
Systemic lupus erythematosus (SLE) & dermatomyositis affects
mainly adult females.
It presents with minor photosensitivity (rash in the malar area
of the face), prominent systemic symptoms.
It is treated
with sun avoidance & Antimalarials