Antihistamines. Most autoimmune urticaria is chronic not acute lasting at least 6 weeks. Many cases resolve over time. Most can be easily managed with daily not as needed antihistamines. Long-acting, non-sedating antihistamines like allegra, Claritin (loratadine) & zyrtec may be taken safely for months or years & will not lose their effectiveness with time. An allergist is the physician to manage this problem.
Acute Urticaria. Control it with oral antihistamines. What type of auto-immune urticaria? Anti-thyroid type or more serious? The main thing is oral non-sedating antihistamines (double to triple the dose) to decrease the itch and it is safe to use Benadryl (diphenhydramine) at bedtime to help her sleep and cut down the itch. If not gone in 6 weeks, see ur allergist.