Can I damage my daughter's health by giving her raw onion juice?

My daughter get asthma whenever she catches a cold, her airways get full of phlegm and she has taken antibiotics many times to clear her chest. In order to stop her having so many antibiotics everytime she starts coughing I increase the brown inhaler to 4 puffs twice a day and I also give 1-2 teaspoons of raw onion juice mixed with sugar or honey. It works because she stops coughing! but I wonder if the onion juice may cause an ulcer in her digestive tract or any other health problem, she is only 7 years old. Thanks for answer!