A red rash under the skin could be a myriad of things like hives, psoriasis, eczema or possibly an allergic reaction to specific plants, foods or medications, according to WebMD. If the problem persists, a doctor's advice should be sought. Since rashes present both above and below the skin in different instances, it could be hard to diagnose exactly what is causing the rash without a doctor's consultation.
Rashes can occur from the result of coming into contact with certain plants including poison ivy, poison oak, poison sumac, wood nettle, stinging nettle or leadwort, according to Christine Bahls for Everyday Health. In the case of a plant-based rash, the remedies vary and could include washing the area thoroughly, applying cortisone cream, using natural poultices or creating a baking soda/water paste.
It is also not unusual for hive-like rashes to be linked to allergic reactions to medications, food or food additives. Extreme temperatures can also irritate the skin and cause a rash to present as can certain viral infections such as strep throat. In the case of ongoing rashes and skin irritations that appear on a more long-term basis, conditions such as eczema or psoriasis could be the culprit. In the instance of a recurring rash, a doctor may prescribe treatments such as shots, oral medications or topical creams and may even recommend dietary changes, notes WebMD.