Here's why:
* Puppy allergens: Puppies have higher levels of certain proteins, like Can f 1, which are the main triggers for dog allergies. They also shed more, and their saliva and urine contain higher concentrations of these allergens.
* Adult dog allergens: As dogs mature, their allergen production decreases. This means they shed less, and their saliva and urine have lower concentrations of allergens.
* Individual variation: Everyone's immune system reacts differently. Some people are sensitive to small amounts of allergens, while others can tolerate higher levels.
So, it's possible that someone might be allergic to a puppy because of the higher allergen levels, but not to an adult dog because the allergen levels are lower.
However, it's also important to note that:
* Allergies can develop over time: Some people may not be allergic to dogs initially but develop allergies later in life.
* Allergies can change: Even if you're not allergic to a specific dog, you might become allergic to another dog or even the same dog later on.
The best way to determine if you're allergic to a dog is to have an allergy test with a doctor or allergist. This can help you identify specific allergens and determine your level of sensitivity.