30th July 2026

Clinical manifestations

Photoallergic reactions are uncommon and occur >24 hours after exposure to the agent. The reaction is categorised as a dermatitis and in most often affects exposed skin, but does have the potential to spread to unexposed areas also. Pigmentary changes are uncommon. 

Common agents responsible for photoallergic reaction:

• Sunscreen
• Non-steroidal anti-inflammatory drugs 
• Fragrances
• Phenothiazines
• Quinine
• Sulphonamides
• Quinidine

Photodermatitis secondary to lemons on both thumbs. Source: Wikipedia.

Image Source: Wikimedia Commons (2018). Photodermatitis, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Photodermatitis.jpg (Accessed 19 May 2025).

Phototoxic reactions are more common but require a large amount of exposure for the reaction to occur. The onset is shorter, occurring between minutes to hours from exposure. It is characterised by a typical sunburn rash only on exposure areas of the body and can also lead to pigmentary changes. Severe cases may develop bullae. 

Common agents responsible for phototoxic reactions: 

• Metformin
• Non-steroidal anti-inflammatory drugs (NSAIDs)
• Sulfonamides
• Vemurafenib
• Voriconazole

Phototoxic reaction secondary to commons rue on the forearm. Source: Wikipedia

Image Source: Wikimedia Commons (2006). Effet de la rue Officinale, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Effet_de_la_rue_officenale.jpg (Accessed 19 May 2025).

• Amiodarone
• Retinoids
• Psoralens