A person becomes allergic when he or she acquires an abnormal immune response to a substance that does not normally cause a reaction. This typically occurs after an initial exposure (sensitization) to the allergen, although multiple exposures to the substance may be necessary.
There is apparently a genetic predisposition to allergies; the incidence is higher in children whose parents also suffer. If one parent is allergic, the incidence is roughly 29 percent and if both parents are allergic the likelihood that the child will have allergies increases to about 47 percent. However, allergies can develop during any stage in life: You are not simply born “allergic.” There is an allergic continuum on which during the course of your life there are times where you are more likely to become allergic than others. Some patients outgrow their allergy, which means that they are no longer affected. Years later, the same allergy might reappear. What’s more, allergies can affect different target organs at different times. This may be the case as the sensitivity of the target organ may change over time. For example, you may suffer from a different pattern of allergy symptoms today than you did 10 years ago, and it may change in the future.
The allergen must enter a person’s body for it to trigger an immune response. This can happen through physical contact (something on the hand that gets transferred to the eyes, nose, mouth, or ears), inhalation, ingestion, or injection (drugs). The next time the exposure occurs, a broad spectrum of inflammatory responses will begin, causing an allergic reaction. What’s happening to your body is this: The immune system that is responsible for protecting the body from harmful foreign substances is presented with a substance that it cannot tolerate. For example, when the immune system is confronted with an allergen such as pollen, it mistakes it for a foreign, invasive substance, even though pollen is not typically harmful to most people. Yet the allergic reaction may be devastating to the point at which it can make the allergic person very sick and can even be deadly.
The typical immune response to any foreign substance - be it a
virus, bacteria, cancer cell, or allergen - is to form an antibody or immunoglobulin to that antigen. For instance, when you contract a strept infection of the nose or throat, a whole series of reactions occur that defend you from that bacteria. Antibodies are formed to the Streptococcus bacteria. They attach to the Streptococcus pneumoniae cell membrane and attack the bacteria directly, while also instructing your white blood cells to attack, engulf and kill the bacteria.
In the case of an allergy, your body perceives the pollen as a threat. You start to form an antibody against pollen. This antibody is called immunoglobulin E (IgE). The IgE binds to white blood cells called mast cells and basophils. Mast cells are found in connective tissue all over the body, especially located near small blood vessels. Basophils are found in the bloodstream. When there is an allergic reaction, these cells migrate toward the nasal membrane. Mast cells and basophils contain histamine and other chemical mediators of inflammation that they release like little explosives. So when pollen enters your body, it comes into contact with the IgE bound to a mast cell or the basophil. The mast cell or basophil explodes, releasing histamine and other inflammatory substances, which cause swelling, heat, and often itching: the allergic response.
There are two phases to the allergic response. The first is an early response, which occurs within seconds of the introduction of the antigen. This immediate response lasts for only a few minutes. The second response occurs when the white blood cells are launched during the inflammatory response. However, symptoms can occur during either the early or the late reaction.
Antigen exposure will lead to itching within seconds, followed by sneezing. A runny nose follows, and within about 15 minutes you will become congested and stuffy. You may also complain about tearing, itchy eyes, sore throat, throat clearing and coughing, itchy throat and ears, and ear popping. Sinus obstruction due to the swelling and congestion can lead to sinusitis, when the connection with CAID begins. Nasal obstruction leads to mouth breathing, snoring, and sleep apnea. Eustachian tube dysfunction may occur, leading to hearing loss, tinnitus (ringing in the ear), and/or dizziness (vertigo). The gastrointestinal tract can then be affected as the infected mucus travels into the stomach, and
you may complain of any of the following symptoms: gas, belching, bloating, indigestion, diarrhea, and ingestional fatigue (a feeling of tiredness following a meal).
In children this can lead to adenoid infections and abnormal dental development. In addition, these children usually have “allergic shiners,” dark circles around the eyes, and swollen eye lids. Children can also develop a horizontal crease along the tip of their nose from rubbing it so often (affectionately called “the allergic salute”).