Rashes that I see develop under the arms are helpful to breakdown by cause:
Irritant contact dermatitis: Think red, itchy, scaly! Irritation can occur with natural deodorants that have too high a concentration of baking soda. Look for products that have a lower concentration of baking soda or options without baking soda. The essential oils in these products can also lead to contact dermatitis. To figure out if it could be the oils, it helps to swatch the product on your inner forearm and see if a rash develops after a day or two. If it does you may have a sensitivity or allergy to one of the ingredients.
Intertrigo or yeast infections: Think red, glossy, peeling from edges and sometimes pus bumps along edges (just like a diaper rash). Whenever we alter the pH of our skin, we change the bioflora (the community of good and bad bacteria and yeast that live on our skin) and sometimes yeast can overgrow. If you start to feel that the area is somewhat raw and uncomfortable it can help to use a little cortisone cream with an over the counter antiyeast cream for a couple of days. If it doesn’t get better you may need to see your dermatologist to clear this.
Heat rash/ chafing: from the extra moisture, the skin can start to feel raw as well. If this is the case, wearing clothing that can wick this moisture away will help. Dri-fit and Dryflex fabrics that are normally in athletic wear and AMBERNOON clothing can help.
Folliculitis: this is a bacterial infection that occurs in the hair follicles. With the bioflora change, sometimes bacteria can overgrow. When we shave we can spread the bacteria in this area. This will look different then the other rashes because the bumps will be based around hair follicles and look like pus bumps that get crusty and scabby. It can help to start with an over the counter anti-bacterial cream and changing your razor.