Remember, you canât out-exercise a bad diet so if youâre eating too many calories each day, it doesnât matter how much walking youâre doing since you will not be able to burn it all off. So, focus more of your attention on the foods youâre eating.
1 Keratosis pilaris causes numerous small, rough, tan or red little bumps around hair follicles on the upper arms, thighs, buttocks, and cheeks.  Keratosis pilaris creates the appearance of gooseflesh, goose bumps, or chicken skin.
Underarm heat rash and sweat rash. Another common armpit skin rash cause is sweat rash which is primarily caused by blocked sweat ducts that âtrap perspiration under your skin. Symptoms range from superficial blisters to deep, red lumps â [mayoclinic.org].nderarm rash due to due to allergic reaction or contact dermatitis. Allergic reactions to various chemicals such as soap, shaving creams, body lotions, cosmetics, certain synthetic clothing material, fragrances, or detergents used to clean your clothes can cause rashes especially red itchy rashes.