Sweaty armpit causes problems of odour. This is affect social interaction subtly. This is especially people generally feel embarrassed to tell you that you have bad odour. You could be going around with people avoiding you but without you knowing.
If you have sweaty armpits, please make sure you put on deodorant daily.
There are 2 types of deodorant. The anti-perspiration type is useful for mild sweaty glands cases. For the more severe once, you need to combine the anti-perspirant one with a anti-bacterial one to prevent odour from forming.
There are generally no side effects to using deodorants.