Sometimes people do get a rash from the deodorant. The most likely cause is irritation from the baking soda. Some people find it helpful to apply a bit of coconut oil or argan oil to the area before applying deodorant to minimize irritation.
Some other tips to reduce irritation:
- Apply to clean skin
- Don't use right after shaving
- Apply a small amount
- Squeeze out 1/8"-1/4" per armpit
- Rub in gently
- Wash off before going to bed every night
Discontinue use if irritation persists.