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Know All About Photosensitivity

Written by
Dr. Suvash Sahu
and medically reviewed by iCliniq medical review team.

Published on Nov 01, 2016 and last reviewed on Sep 07, 2018   -  2 min read



There are certain chemicals and drugs that induce photosensitivity, which mimic other skin diseases. The basic knowledge about this is essential to eliminate the illness.

Know All About Photosensitivity

Photosensitivity induced by exogenous agents can be divided into phototoxicity and photoallergy. Phototoxicity is the result of direct tissue and cellular injury caused by the phototoxic agents and radiation. It can occur in all individuals, provided the dose of the agent and inducing wavelengths are adequate.

In contrast, photoallergy is a delayed type hypersensitivity response to a molecule that turns antigenic on absorption of photons. It has a sensitization phase, an incubation period of 7 to 10 days following the first exposure. Thus, it occurs only in previously sensitized individuals and requires only minimal concentration of the photoallergen. Though several medications have been reported to cause photosensitivity, the exact prevalence of the same in the general population is unknown.

Phototoxic Agents:

  • Systemic phototoxic agents - Voriconazole, Griseofulvin, Chloroquine, Quinine, Sulfonamide, Tetracyclines, Quinolone, Furosemide, Thiazide, Azathioprine, Methotrexate, Alprazolam, Phenothiazine, etc.
  • Topical phototoxic agents - Fluorescein dye, Fluorouracil, Furocoumarins, retinoids, rose bengal and tar.


  • Systemic photoallergens - Drugs such as Griseofulvin, Quinine, Quinolone, Enoxacin, Quinidine, Ketoprofen, Piroxicam and Pyridoxine
  • Topical photoallergens - Sunscreen ingredients include Benzophenones, PABA (para-aminobenzoic acid), Avobenzone and fragrances such as 6-Methyl Coumarine, musk ambrette and sandalwood oil.

Clinical Features:


Acute phototoxicity develops within hours following exposure to a topical or systemic phototoxic agent and appropriate UVR (ultraviolet radiation). Erythema, edema as well as burning and stinging sensation characterize the initial presentation with vesicles and bullae seen in severely affected patients.


Pruritic eczematous eruptions in photo distributed areas in a sensitized individual within 24 to 48 hours after exposure to the photoallergen and sunlight. Vesicles and bullae may develop in severe photoallergy.

Patient Evaluation:

  • Most important is the history of exposure to known photosensitizers.
  • Whether window glass filtered sunlight (UVB is filtered out by window glass) can induce cutaneous eruption is to be ascertained as the action spectrum for phototoxicity is usually within UVA range.
  • The distribution of the cutaneous eruption is a useful clue to the type of responsible photosensitizer. Widespread eruptions are suggestive of phototoxicity induced by systemic photosensitizers and localized eruptions are suggestive of photoallergic contact dermatitis induced by topical photosensitizers.
  • Vesicular and bullous eruptions, most commonly associated with phototoxicities are accompanied by a burning sensation.
  • Eczematous eruptions strongly suggest photoallergy and pruritus is a usual feature.


Avoidance of photoallergens and phototoxic agents is the mainstay of treatment. For already erupted lesions, one should get evaluated and depending on the severity, it can be treated with topical or systemic steroids for shorter duration.

For better understanding of photosensitivity consult a cosmetologist online -->

Last reviewed at:
07 Sep 2018  -  2 min read


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