Started atibiotics 2 days ago for tonsillitis. Outer vagina started itching today very bad. Left inner labia is swollen and red. Yeast infection?

Could be. Some women are more prone to yeast infections while taking antibiotics. The itching can be intense and you may notice a "cottage cheese" type of discharge from the vagina. Try an over the counter treatment and if it does not improve, call your physician who can further evaluate you and prescribe Diflucan (fluconazole) if needed. In the future, if you need antibiotics take acidophilus which can lessen the ris.