Food allergies develop when the immune system mistakenly identifies a specific food protein as a dangerous invader. Symptoms of food allergies are caused by the immune system’s inflammatory attack on the food protein.

Most scientists believe food allergies are probably caused by a combination of inherited and environmental factors. Still, no one has identified why some people develop food allergies and some people don’t.

Risk Factors for Food Allergies

It is important to note that while science is good at finding correlations, or apparent relationships, between factors and disease, correlation does not prove that the factor causes the disease. Many risk factors for food allergies have been identified and are being studied, but none have been pinpointed as the cause of food allergies.

Age is a factor in the development of food allergies. Younger children are more at risk for developing food allergies than are older people.

Hereditary Factors

People are more likely to develop food allergies if a close relative also has food allergies. People with food allergies are also more likely to develop other immune-related conditions including asthma and eczema. These three related conditions — allergies, eczema, and asthma, known as the “atopic triad” or “atopic march” — tend to run in families.

According to a large study published in the Journal of Allergy and Clinical Immunology, women are more likely to have food allergies than men — 4.2 percent versus 2.9 percent — except for peanut allergies, which were slightly more prevalent in men. The same study found that people of Asian descent were more susceptible to developing food allergies than people from other ethnic backgrounds.

Approximately 35 percent of people with food allergies also have atopic dermatitis (eczema), an immune-related disorder in which the skin’s barrier is disrupted. Genes that influence skin absorbency may contribute to atopic dermatitis. A new theory about the development of food allergies suggests that the immune system becomes sensitized to foods when babies receive early exposure to the foods via their skin. If babies with vulnerable skin are kissed and touched by people with food on their hands or mouths, the theory suggests, perhaps the proteins absorb into the baby’s skin, and the immune system interprets the food proteins as dangerous invaders.

Environmental Factors

One theory suggests that the increase in food allergies in the modern era is caused by disruption in the balance of microorganisms that colonize the gut. The modern Western lifestyle includes improved sanitation, less exposure to farm animals, increased antibiotic use, more vaccinations, and a diet with processed foods. Perhaps this lifestyle has triggered changes in our gut bacteria that has led to greater food intolerance.

Another theory under consideration links low levels of vitamin D, including sunlight, with an increased risk for developing food allergies.

Condition Guide

• Food Allergies: An Overview
• Food Allergy Symptoms
• Food Allergy — The Path to Diagnosis
• Food Allergy vs. Food Intolerance: Are They One and the Same?
• Medications for Food Allergy Symptoms
• Types of Food Allergies