My 3-year old daughter w/ CF has broken out into a severe rash with several hives. It is itching her pretty bad, and topical cream has not cured the situation. My wife and I noticed it when she returned from the backyard...it may be due to a bug bite or allergy to the fresh cut grass. I was told to never give her an antihistimine because this has a a negative impact on the mucus in her lungs by drying it up and possibly increasing her chances of another infection. Is the true w/ just a single time small dose? Can we use an antihistimine to stop the outbreak? Thoughts? Thx!!