As I was contemplating the topic for this issue, my family started asking me allergy questions. I decided to take that concept and turn it into a column. What we have here is a series of allergy questions that patients often ask me in the office. At first, they may seem a little disjointed, but I promise you there is a common theme, which I will tie together at the end.
Q: Why am I only allergic to specific plants, animals or foods?
A: To be allergic to a specific antigen, your body needs to make antibodies to that specific allergen. The antigen is a protein contained somewhere on that plant or animal that makes its way into your body. In the case of plants or molds, the pollen or the spore needs to become wind borne and inhaled into your nose or lungs or blown into your eyes. In the case of animals, it is the dander or the saliva which comes into contact with your body. In the case of dust mites, it is the fecal particles from the mites which come into contact with your body. In the case of foods, the antigen needs to be ingested. Your body then needs to mount an immune response to the antigen. This depends on your genetic tendency to be allergic, the degree of sensitivity and the amount of exposure.
Q: Why am I allergic to raw peanuts, but not to peanut oil?
A: First of all, be careful. Even peanut oil can be dangerous. The peanut allergen is the protein found in the peanut. The oil itself is not allergenic; however, trace amounts of the protein can be found in the oil. Heating, cooking or chemically processing a food breaks down most of the proteins; however, there is no guarantee of safety with hot peanut oil. Antihistamines and injectable epinephrine should always be available.
Q: What is the difference between milk allergy and lactose intolerance?
A: Milk allergy is an immune reaction to the milk proteins, casein or lactalbumin. The symptoms can be gut related or skin related, but can also be classic ear, nose and throat symptoms, as well as asthma. Lactose intolerance is a genetic deficiency of the enzyme lactase, which breaks down the milk sugar lactose. The symptoms are limited to the gut.
Q: Can I be allergic to perfumes, gas fumes or smoke?
A: Technically, no, but you can experience similar symptoms to allergies. These are chemical sensitivities. They are not true allergies. They are not immune reactions to a foreign protein. In reality, they are toxic reactions. They can cause nasal congestion, runny nose and post-nasal drip, just like true allergies.
Q: It’s winter. Allergy season is over. Why do I still have symptoms?
A: Allergy season is never over in Virginia. December and January give us a short break from the pollens, but indoor allergens are year-round. Dust mites, pets and molds contain allergenic proteins, as well.
So, what’s the common theme here? Well, it’s the protein. An allergic patient makes antibodies to a foreign protein. This causes the release of compounds responsible for the allergic reaction, such as histamines and leukotrienes. Allergy shots build up blocking antibodies, which remove the foreign protein without causing a reaction.