How long do topical corticosteroids take to work for heat rash?

Heat rash develops when blocked sweat ducts trap sweat in the skin. A corticosteroid can reduce inflammation, but it does not remove heat, moisture, tight clothing or friction. If those conditions continue, new bumps may appear. A rash that is painful, widespread, draining or unusually persistent may be something other than simple heat rash and deserves assessment. Read more about Heat Rash if you are unsure of the pattern.

Move to a cooler environment, wear loose breathable clothing and keep the area dry. Wash gently, pat rather than rub, and avoid heavy ointments or fragranced products unless advised. Use the corticosteroid only if a clinician or pharmacist has recommended it for this rash, following the label or prescription. Avoid applying it to broken skin, the face or skin folds unless specifically told to do so. Treatment information is available in Topical Corticosteroids.

Seek care promptly for fever, marked pain, pus, spreading warmth or swelling, or a child who seems unwell. Arrange an assessment when the rash does not start settling after cooling measures and the advised treatment period, or when it repeatedly returns. These features can point to infection, another inflammatory condition or a heat-related illness.

Ask whether the rash fits heat rash, whether a steroid is needed, and which area and duration are appropriate. Clarify how to prevent recurrence during hot weather and which signs mean the diagnosis should be reconsidered.