Doxycycline (tetracyclines) and Photosensitivity reaction: is the FAERS signal real?
Doxycycline (tetracyclines) ↔ Photosensitivity reaction
Doxycycline is one of the most phototoxic antibiotics: it accumulates in the skin, absorbs ultraviolet light, and produces an exaggerated sunburn-like reaction on exposed areas. It is a genuine, well-characterised chemical phototoxicity rather than an allergy, and it is common enough that sunscreen and sun-avoidance counselling is standard when the drug is prescribed. The 427 co-reports (PRR 8.2) reflect both the real effect and doxycycline's very wide use for acne, tick-borne infections, and malaria prophylaxis.
Regulatory basis: doxycycline prescribing information (photosensitivity warning; sun-protection advice). Established tetracycline phototoxicity literature.
| Bradford Hill viewpoint | Status | Note |
|---|---|---|
| Temporality (necessary) | met | The reaction appears during sun exposure while taking the drug and settles after withdrawal |
| Strength | partial | PRR 8 with a moderate co-report count |
| Consistency | met | Reproduced across tetracyclines and in dermatology practice |
| Specificity | met | Drug-induced phototoxicity has a characteristic photodistributed pattern |
| Biological gradient | partial | Broadly dose- and exposure-related (drug dose and UV exposure) |
| Plausibility | met | Ultraviolet absorption by the drug in the skin is the defined mechanism |
| Coherence | met | Coheres with the routine sun-protection counselling given with doxycycline |
| Experiment | partial | Dechallenge (withdrawal plus sun avoidance) resolves it; no randomized trial |
| Analogy | met | Analogous to phototoxicity with other tetracyclines and some other drugs |
This page's own qualitative read, not an automated/citation-gated assessment.