Injecting the immune system with lab-made antibodies may better prepare it to fight against cat allergies than regular allergy injections alone. Combining asthma medication with allergy shots may be effective in treating cat allergies. Allergy symptoms were also decreased for up to a year after treatment ended, according to recent research. Immunotherapy, or allergy injections, has been used for over a century to alleviate allergy symptoms including itchiness, watery eyes, sneezing, a runny nose, and congestion.