Allergies are the body’s reaction to what it perceives as a harmful substance.
Allergies present in many ways and are caused by food or the environment your dog is in.
Typically no. However if your dog has an extreme reaction you should seek immediate medical attention to your dog.
Your vet will ask you about what foods and household items your dog has recently been exposed to. Allergies to food are typically diagnosed by elimination diets. Your vet would suggest eating simpler food such as one type of protein and one type of carbohydrate for 8-12 weeks. Environmental allergies may be a little more different, removing certain dog beds, or changing laundry detergents may be suggested, or major lifestyle changes. It is important to note, that some allergies are never pinpointed with testing.
Dogs may also experience seasonal allergies during high pollen weather. Your dog may also be allergic to dust. If you just went through a major house cleaning (or maybe you need to do one) your pup may have issues.
The best way to treat an allergy is to avoid the thing the dog is allergic to. If you cannot figure out what your pup is allergic to there is allergy medication your vet can prescribe.