Playing with Others: Similac

Allergic to Formula?

I have been pumping and feeding my 5 month old breast milk up until now, but my milk supply is dwindling, and I am ready to put her on formula. We tried Similac formula and she just threw it up every time. I have been adding 2 ounces Parent's Choice milk based formula into her bottle for about 5 days now and her nose is extremely stuffy and she coughs up mucuous. I am thinking that she is allergic to the milk, but what formula could I give to her? Or will she just get over it and get used to the formula? (She was premature and never...