Dermatology - Drug Induced Photosensitivity

​Dermatology - Drug Induced Photosensitivity 
When a photoallergen and sunlight are exposed to sensitized persons, it causes a pruritic eczematous eruption that is limited to the exposed locations. This condition is clinically similar to allergic contact dermatitis. The eliciting chemical or medicine has typically been delivered topically to the patient, however systemic elicitation can also happen.

The sores are quite itchy, and they can be mistaken for allergic contact dermatitis clinically.
The lesions are crusty, scaling, vesicular, and papular. Similar to lichen planus, lichenoid eruptions can also occur occasionally. Scaling, lichenification, and severe pruritus resembling atopic dermatitis or, once more, chronic allergic contact dermatitis are symptoms of chronic drug photoallergy. The distribution pattern of photosensitivity indicates that lesions are mainly limited to light-exposed areas, while they may also spread to nearby nonexposed skin. The fact that the upper eyelids, the space beneath the nose, and the small strip of skin between the lower lip and the chin are frequently spared (shaded areas) is helpful in the diagnosis process.
When photoallergic dermatitis becomes chronic, the ailment worsens with each subsequent UV exposure and continues even when the photoallergen that caused it is removed. The consequence is extremely irritating, lichenified confluent plaques that resemble chronic dermatitis. These plaques can cause deformity and discomfort for the patient. Avoidance of photoallergens does not heal the sickness since the condition is now independent of the original photoallergen and is made worse by every new solar exposure.

The photopatch test is used to confirm the diagnosis, which is based on the patient's medical history, the eruption's pattern of allergic contact dermatitis, and the eruption's restriction to sun-exposed areas.


Sunlight and allergy avoidance are therapeutic until the illness progresses to a chronic state. Immunosuppression (azathioprine + glucocorticoids or oral cyclosporine) is necessary in severe cases.