Why do I get heat rash on vacation?
Last updated September 3, 2026.
Because your sweat glands have not acclimatized: miliaria is blocked, inflamed sweat ducts - backed-up sweat raises the itchy bumps - and it thrives in hot humid climates, the exact shock of flying a temperate body into tropical heat with sunscreen layers and all-day sweating. Classic pattern: days 2 to 4 of the trip, under waistbands and in skin folds, resolving once skin cools and dries. Care: loose fabrics, cool showers, AC breaks, no heavy creams on the rash, calamine for itch. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What to do
- Cool and dry the skin: showers, AC breaks, loose breathable clothing.
- Skip occlusive layers on the rash: heavy creams keep the ducts blocked.
- Calamine or mild hydrocortisone for the itch: days, not weeks, to resolve.
- Get seen if: the rash spreads fast, turns angry, or arrives with fever - infection, not prickly heat.
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