How do tetracyclines cause phototoxic skin reactions?

Tetracyclines absorb UV-A light in the skin

UV exposure excites the drug molecules

Excited tetracyclines generate reactive oxygen species ROS

ROS damage keratinocytes and skin cell membranes

This leads to sunburn-like inflammation

It occurs without immune system involvement

Damage happens rapidly after sun exposure.

Skin redness and edema appear first.

UVA penetrates deeper than UVB increasing risk.

Cellular DNA damage contributes to symptoms.