Best OTC for severe poison ivy around face neck ears and hands? Can it be dangerous and what to watch for if so?

See your physician. Based on your description, this is far more severe than what otc Hydrocortisone can handle. Severe rash and breakdown of the skin can lead to an infection of the skin, that can be disfiguring or fatal. Health care can be expensive, but lack of health care leads to complications that are even more expensive to treat once you have no choice but to go in. See your doctor.
OTC RX FOR POISON IV. Benadryl (diphenhydramine) every 4 hours to stop the itching, but ba careful will make you drowsy, calamine lotion and over the counter 1%hydrocortisone cream twice a day. But if it is severe and since you say face is involved, you should see your doctor as you may need systemic steroids by mouth for up to six days. It can get secondary infection and leave some scaring if not properly treated.