Phototoxicity and Rash Development in Travelers

Primary Mechanism: Phototoxicity

Doxycycline causes photosensitivity reactions manifesting as exaggerated sunburn-like symptoms including burning, erythema, and potentially large-area photodermatitis when exposed to sunlight, with the CDC warning patients to avoid prolonged direct sun exposure and use UVA-absorbing sunscreens 1
The American College of Physicians and other guideline societies imply that patients taking tetracyclines like doxycycline should avoid prolonged direct sun exposure and use UVA-absorbing sunscreens, as doxycycline is the most likely culprit for causing a rash after returning from holiday, primarily due to its well-documented phototoxicity when combined with sun exposure during travel 1

Co-amoxiclav (Augmentin) can cause drug-associated rash, with an estimated 8 cases of rash (including 1 severe life-threatening reaction) per 10 cases prevented when used prophylactically, according to the Infectious Diseases Society of America 2
Cephalexin is specifically noted as preferred over tetracyclines for patients with photosensitivity concerns, and is not associated with phototoxic reactions, as suggested by the American Academy of Dermatology 1
Macrolides like clarithromycin and erythromycin are not typically used for travel prophylaxis, and have no specific photosensitivity documented in the provided evidence, according to the European Society of Clinical Microbiology and Infectious Diseases 3