The first and the easiest method is to apply a hot compress to the area where there are ingrown hair. A simple way could be to take a washcloth, dip it in hot water and apply it on the affected are for five to ten minutes. This will help in the reduction of swelling and also make the exodus of puss (foul yellow liquid deposit) easier.
Another very good technique is to exfoliate your under arms on a daily basis. Using loofah or body scrub, you can gently remove the dead skin.
Acne treatment cream can also be applied to your ingrown hairs. These creams contain benzoyl peroxide, which not only helps in skin regeneration (thus bringing the hair surface up), but also kill bacteria, which can worsen your ingrown hair condition. Bacteria can also be killed by cleansing your arm pits and under arm area with an antibacterial cleanser, a toner or an astringent.
Hydrocortisone cream can also be used to reduce inflammation and irritation, which will help in the quick healing.