Bumps in a line on the skin: possible causes

The arrangement matters, but it is not a diagnosis by itself. Bumps around hairs may fit folliculitis, while fine rough bumps can occur with keratosis pilaris. Heat, sweat and blocked ducts may produce heat rash. Firm pale bumps can be milia. A line that is intensely itchy, scaly or violaceous may need assessment for an inflammatory condition such as lichen planus. Consider whether the bumps appeared after a new product, exercise, friction, plants or an insect exposure. Note whether they are painful, fluid-filled, scaly, spreading or limited to one area.

Do not scratch, pop or scrape the bumps. Clean gently, keep the area cool and dry, and stop any newly introduced cosmetic, detergent or topical product until the pattern is clearer. Loose clothing can reduce friction. A cool compress may ease itch or heat. Photograph the area in good light and record when it began, what changed beforehand, and whether new bumps are appearing. Avoid applying steroid, antibiotic or antifungal products without advice when the cause is uncertain; the wrong treatment can obscure the pattern.

Arrange an examination if the line persists, spreads, repeatedly returns, bleeds, crusts, or changes in colour or texture. Seek prompt care for severe pain, facial or eye swelling, breathing difficulty, fever, rapidly spreading redness, or extensive blistering. An itchy rash affecting household members or appearing in typical contact areas also deserves assessment. A clinician may recommend an antihistamine treatment for an itch-driven pattern or cryotherapy for a suitable individual lesion, but the choice depends on the diagnosis.

What features make this pattern more consistent with irritation, folliculitis, a bite or another condition? Do I need an examination or skin test? Which products should I stop, and what can I use safely for itch?