What are some common signs of an allergic reaction in pets?

Itching, swelling, redness, or gastrointestinal upset are indeed common signs of an allergic reaction in pets. Allergies can manifest in several ways, and the skin reactions, including itching, redness, and swelling, are particularly notable as they indicate that the body's immune system is responding to a perceived threat. When pets come into contact with allergens—like certain foods, pollens, or flea bites—these symptoms can occur as part of an inflammatory response. Gastrointestinal upset may also happen in cases of food allergies or intolerances, as the body attempts to eliminate the allergen.

The other choices present symptoms that are not specifically indicative of allergic reactions. For example, vomiting and diarrhea might suggest a gastrointestinal issue or infection rather than an allergy. Loss of appetite, excessive barking, and changes in sleep patterns could signal stress or discomfort but are not directly linked to allergic responses. Skin infections, hair loss, or weight gain suggest other health issues, rather than allergies specifically.