Bird allergies cause allergic reactions in people who spend a lot of time around birds and birdcages, and who become sensitized to the allergens associated with feathers, dander and fecal matter.

An allergic reaction is the immune system’s attempt to defend the body from a perceived threat that, in reality, is harmless. During this process, a foreign substance called an allergen comes into contact with the body and triggers the immune system to produce antibodies. 

Each antibody is specifically designed to attach to and attack a particular antigen. The antibody that responds to allergens is called immunoglobulin E (IgE). As IgE defends the body, it coats and activates mast cells. These cells respond by bursting and releasing the chemicals that trigger an allergic reaction, producing symptoms such as itchy eyes, runny nose and sneezing. In some cases, the reaction is more extreme, resulting in hives, eczema (skin inflammation) or breathing difficulties.

As with all animal allergies, dried dander ­– known as “feather dust” in birds – is a major trigger for those who suffer from bird allergies. Birds have three types of feathers – contour, down and flight. Down feathers have short shafts, and serve to keep the bird warm by trapping air close to the body. These feathers disintegrate slowly into dander.

As a bird preens, shakes its body or ruffles its feathers, it kicks up dander and sends it into the air, where it can be inhaled by humans. Feather dust is also found in products that use bird feathers, such as pillows, comforters and down jackets.

Bird droppings can also trigger allergies in susceptible people. Most people with bird allergies experience relatively minor symptoms associated with allergic rhinitis (hay fever). However, others experience more substantial forms of this allergy, such as:

• Hypersensitivity pneumonitis. Also called allergic alveolitis, this is a complex syndrome rather than a single disease. Repeated inhalation of dust containing organic antigens triggers several diseases, including bird fancier’s lung (also known as pigeon lung disease or pigeon breeder's lung). Feathers, droppings and feather dust from birds and birdhouses are the major sources of this disorder, which produces asthma–like symptoms and decreased lung capacity in humans. It afflicts bird keepers and others who spend large amounts of time around many birds. Hypersensitivity pneumonitis can occur in one of three forms:
  
  
• • Acute. Affects the individual within four to eight hours after inhalation of a high level of feathers, feather dust and/or droppings. Symptoms usually cease when exposure is ended.
    
    
  • Subacute. Results from long-term exposure. Ending exposure also tends to relieve symptoms.
    
    
  • Chronic. A nonreversible form of bird fancier’s lung can take hold when subacute exposure continues.
    
    
• Bird-egg syndrome. People who are allergic to eggs may also have their allergy triggered by inhaling bird antigens. As the body becomes sensitized to bird allergens, the individual reacts to exposure to bird antigens or egg intake.