1. Heat rash (miliaria rubra): sweat ducts become blocked, often after heat, humidity, exercise, tight clothing, or prolonged sweating.
2. Mild folliculitis: irritation or infection of hair follicles, often triggered by sweat, friction, shaving, oily products, tight synthetic clothing, or sometimes a hot tub.

What to do now

• Keep the area cool and dry. Wear loose, breathable cotton clothing.
• Shower after sweating and change out of workout clothes promptly.
• Avoid tight waistbands, heavy/oily creams, scrubbing, and picking.
• Pause shaving or hair removal over the area until clear.
• Use a gentle, fragrance-free cleanser.
• If itchy, use cool compresses or calamine. A pharmacist or clinician can advise whether a short course of 1% hydrocortisone is appropriate. Avoid using steroid cream if bumps become pustular, painful, or clearly infected.
• If the bumps are pustular or persist, a clinician may consider a medicated wash or prescription topical treatment. Do not start oral antibiotics without an examination.

Seek medical assessment promptly if

• Fever, feeling unwell, rapidly spreading redness, warmth, swelling, or significant pain
• Pus, boils, crusting, or red streaks
• Rash after a new medication, with facial swelling, mouth sores, or breathing difficulty
• Spots are purple/non-blanching, meaning they do not fade when pressed
• No improvement in 7-14 days, frequent recurrence, or diabetes/immunosuppression.