This is what I have done.
First, there is no quick fix. Start with diet, I find I need more oil In my diet.
If you have allergies towards any of these foods, avoidance is the best. (I am allergic to coconut). Try eating a avocado a day, or drizzle extra virgin California olive oil on your food. Add coconut oil your coffee.
To that, add pineapple (natural anti inflammatory). Where cotton clothing. When you wash your clothing rinse 2 or more times, just get excess soap out.
Use a fabric softener you like,( I like bounce).
When you shower, don't use hot water, and don't stay in long. I find showering every other day, but if you sweat, the salt from you body can be a irritant, (it is for me). Shaving can be an issue for me. So be sure to change your shaver as soon as it gets dull(you must be your own bestfriend here), water dulls your blades, so dry it off when done.
In all my pit areas I like to use a dissolving exfoliant with citrus and clean wash cloth. My soap I like to use Tea Tree oil soap,( may be known as Green Tea Tree body soap) you need to find what best works for you- this is what has faithfully worked for me. (Meluleuca, Trader Joe's) these are companies I use. If I don't use these I break out bad. Tea Tree is very drying but it is anti fungal, antibacterial, antiseptic. Never using moisturizing soaps or moisturizers in pit areas. If they do wash with Tea Tree soap.( for me a must). Dry with a clean dry well rinsed cotton towel. Before putting on clothes, be sure all pit areas are completely dry (I use my ceiling fan) This is when I put on my CeraVe lotion or olive oil(from my kitchen). Being careful not to get in any pit areas, nor bends of elbows or bends of knees, nor feet.
And strive to always wear cotton. If I break out I use on my breakouts, Tea Tree oil (Trader Joe's or Meluleuca ). Hope this helps you as it has helped me. My God bless you with wisdom in caring for you and your family,blessings ❤💕

I have it under my armpits as well. I mix half cornstarch & half baking soda in a small container. I use a blush makeup brush to apply it. It keeps me dry & my arm pits dont smell. I live in hot Arizona.

I have learned since last discussion. I have sever reactions to Parabens. Cerave lotions and Aveeno have Parabens. These cause a 3 month long, pain intense, persistent itch that will not go away no matter what I do. So avoidance is best for me. Allowing air, and keeping area dry also helps. Try not to fear, nor be anxious, (I get it, hard to do but fight the urge) but in these hard areas in our life. Seek peace in you. Knowing this is going to take time. So this is how we fight for ourselves.
Remember to use fresh clean towels to dry yourself. Even using a fan, not the blow dryer to help dry yourself. ( the blow dryer uses many components to dry hair. Not ment for parts that remain covered and generally don't see the son) we have delicate skin. This is our normal. Don't upset it. Feed, fuel your body, it's your learn it. We can't put Diesel in our gas cars, so don't put stuff that cause our body issues. Or we can suffer. Avoidance is best. Take a good probiotic. Avoid all known allergens. Talk to a good pharmacist, they can be valuable. They know meds, chemicals, reactions... most doctors don't know this quite as well as Pharmacist. Wear 100% cotton. And journal all you are doing. Eating, all the chemicals in your shampoos, conditioners, lotions, creams. Make a list, and find out what they are, what do they do. Begin eliminating those chemicals that are suspected or know that cause you reactions. Even in foods. Avoid them, learn to make your own, when you can.
Hope this helps, this is what I do, to make my life better.
Blessings
These are the things

I have the same issue it was fragranced deodorant so I switched to Dove sentive and has been working for me no smell plus it stops me from sweating win win. I also at night shower with dove sensitive body wash don't put deodorant on to give my skin time to breathe and I use the eczema cream my Dr. Gave me and anti- itch cream with healing works great! Hope this helps.

Shower daily and you will not need deodorants,BO is caused by bacteria when you do not wash your armpits often. Keep it dry also or use baking soda powder.