Swollen lymph node in arm pit

Hello sandylyn,

Welcome to the EmpowHER community. Thank you for reaching out to us about the lump under your right arm.

I am wondering if this is a sebaceous cyst that became infected.

A sebaceous or epidermoid cyst is a noncancerous small bump beneath the skin. Epidermoid cysts can appear anywhere on the skin, but are most common on the face, neck and trunk.
Cysts can become infected and painful.

I suspect that is why the bump initially decreased in size once you started taking the antibiotic.

Speak with your physician. Incision and drainage of the lump may be necessary.
With this method, your doctor makes a small cut in the cyst and gently squeezes out the contents. This is a fairly quick and easy method, but cysts often recur after this treatment.

Your doctor can remove the entire cyst. You may need to return to the doctor's office to have stitches removed. Minor surgery is safe and effective and usually prevents cysts from recurring.

Another option is using a carbon dioxide laser to vaporize the cyst. It results in minimal scarring.

Hope this information is helpful. Please keep us updated.

Regards,
Maryann