Polymorphic light eruption (PLE) is the most common idiopathic photodermatosis. Its action spectrum most commonly lies in:

• A UVC (200–290 nm)
• B Visible light (400–700 nm) only
• C UVA (320–400 nm) or combined UVA/UVB ✓
• D Infrared radiation

Explanation

In polymorphic light eruption, the action spectrum most frequently lies in the UVA range (320–400 nm) or combined UVA/UVB, which explains why it can occur through window glass (which blocks UVB but transmits UVA) and why conventional sunscreens that only protect against UVB may be insufficient. The eruption—papules, papulovesicles, or plaques on sun-exposed skin—characteristically appears 30 minutes to hours after sun exposure and resolves with avoidance. It shows 'hardening' (tolerance) with repeated UV exposure.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.