Food allergy may be associated with hayfever, bronchitis, asthma, and even some forms of pneumonia.
Hay fever
Hay fever with spasms of sneezing and watery nasal discharge may be caused by certain foods, but more common causes are house dust and animal danders (or dandruff). Once again, cow's milk is often responsible, especially in very young children, although it can cause problems in older children and adults as well.
Asthma
The role of food allergy as a cause of asthma may be underestimated because of difficulty with diagnosis. It is possible that food allergens can cause the typical narrowing of the airways associated with asthma, but only several hours after food has been eaten, so that the relationship between a common food and the beginning of symptoms may not be obvious. The most likely causes include milk, eggs, wheat and soya products. Wheezing due to cow's milk usually begins early in an allergic person's life, but the cause-effect relationship often goes unrecognised for long periods. A diet which eliminates the allergen is necessary to confirm the diagnosis.
Recurrent pneumonia
One form of recurrent pneumonia has been shown to be due to cow's milk allergy. This illness, known as Heiner's Syndrome, is what doctors now suspect when children who drink cow's milk suffer from re-current or chronic lung disease. The problem is caused by the fact that they have a very high level of antibodies to the milk in their blood; most symptoms disappear within a few days on a milk-free diet.