When an allergen test is done through a blood test, the allergen will traditionally be labeled with a Class 0 to Class 6 ranking.
Class 0 indicates that the allergen level was undetectable, while Class 6 indicates that the allergen level had a strong positive.
Allergen results are determined based on the number of IgE antibodies in the blood specific to that particular allergen.
For dog allergies, the IgE antibodies would correspond to proteins found in dog dander and saliva.
Class 0 Allergy to Dogs
A Class 0 allergy indicates that the IgE levels were undetectable in the blood. This occurs when the levels were less than 0.35.
If a person has a Class 0 result on their allergy test for dog allergies, it can be assumed that they have no sensitivity whatsoever to dog dander.
Blood tests will typically screen for more than one allergen at once. Some blood tests will analyze up to ten allergens at once.
Unlike a skin prick test, blood tests take several days to process.
They tend to be as accurate as a skin prick test, but they don’t require multiple needle pricks, they don’t react to medications, and they don’t have the potential to aggravate skin flareups.
Class 1 Allergy to Dogs
A Class 1 allergy indicates that there were some IgE antibodies discovered, but that they aren’t present enough to qualify as a positive test. This refers to levels between 0.35 and 0.70.
When a person has a Class 1 allergy, this means that their blood test was inconclusive. Sufficient antibodies are present to indicate that they have a sensitivity.
However, a sensitivity isn’t the same as a full-blown allergy. Most people with a Class 1 rating would not be considered to have an allergy.
However, their reactions to the allergen may become more pronounced if they’re also exposed to substances they truly are allergic to.
For example, a dog owner might not be allergic to dogs, but might be allergic to pollen. In the spring, they may find themselves sneezing more often when in the room with their dog.
It’s possible that their sensitivity to dog fur has manifested as an allergy, but the real trigger is the pollen outside.
Class 2 Allergy to Dogs
A Class 2 allergy is a positive result, with IgE antibodies in the blood between 0.71 and 3.50. It’s the least severe conclusively positive result.
When a person has a Class 2 allergy, they can expect their allergic reactions to be mild and easily treated. It’s common for people to experience a runny nose and watery eyes.
Other symptoms, like coughing and shortness of breath, may occur less frequently.
A person with a Class 2 allergy to dogs would generally only experience allergies after coming into physical contact with a dog.
They may also have a mild allergic reaction if there’s a great deal of dog dander in their environment.
However, these allergies can generally be treated through over-the-counter medications, without the need for immunotherapy or prescription medications.
Class 3 Allergy to Dogs
A Class 3 allergy spans IgE antibody levels of 3.51 to 17.50.
People with a Class 3 allergy are slightly more allergic than those with a Class 2 allergy. As such, they may experience more moderate allergic reaction symptoms.
Their allergies may also be more difficult to control.
Some people with a Class 3 dog allergy may need a prescription medication if they own a dog. It’s best to talk to an allergist or general practitioner about what treatments and therapies are best.
It’s also important to make sure the dog is bathed and groomed regularly.
People with Class 3 allergies should keep their dogs out of their bedroom. They may also benefit from investing in an air purifier.
Class 4 Allergy to Dogs
A Class 4 allergy is the first severe allergy class, with IgE levels of 17.51 to 50.
People with severe allergies should generally not have pets. Class 4 allergy sufferers may experience symptoms not only around dogs, but also around people who have recently been around dogs.
They’re particularly sensitive to dander in the air, even when there’s no actual dog present.
Severe symptoms tend to include shortness of breath and skin rashes. When around dogs, allergy sufferers might find themselves wheezing.
Severe allergies can be dangerous for people with asthma, as the allergic reaction can trigger intense asthma attacks.
People with Class 4 allergies should talk to their doctors about how to handle their allergy.
Class 5 Allergy to Dogs
A Class 5 allergy refers to IgE levels from 50.01 to 100.0.
Class 5 allergy sufferers have the second most severe category of allergy. This indicates an abnormal amount of IgE levels in the blood.
The amount of histamine released upon contact with a dog can cause potentially life-threatening reactions. It’s very rare for anyone with a dog allergy to have a Class 5 or Class 6 allergy, but it isn’t unheard of.
People with Class 5 allergies risk going into anaphylactic shock if they come into direct contact with dogs. If the allergy is severe enough, their doctor will recommend that they carry an Epi pen.
Class 6 Allergy to Dogs
A Class 6 allergy is the most severe allergy, and refers to any blood tests that show IgE levels of greater than 100.0.
It’s almost unheard of for someone to suffer a dog allergy this bad. The vast majority of people have mild to moderate allergies.
In cases where dog allergies do meet this criteria, the person almost always has other severe allergies as well.
This could indicate that the individual had a genetic predisposition to allergies, which then exacerbated the dog allergy.
People with Class 6 dog allergies should stay away from dogs and their handlers at all costs.
Resources:
https://www.mtw.nhs.uk/wp-content/uploads/2015/08/Allergy_diagnosis_reference_guide.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4755411/
https://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/60108
