Allergies

Symptoms of Allergies

Allergy symptoms vary depending on where the allergen enters the body and the strength of the allergic reaction that occurs. Symptoms may include:

• Sneezing
• Coughing
• Wheezing
• Constriction of the airways, sometimes accompanied by asthma.
• Swelling and inflammation of the nasal tissues and sinuses.
• Blockage, feelings of fullness, or pain within the ears.
• Redness and itchiness of the eyes (conjunctivitis).
• Rashes, eczema, or hives appearing on the skin.
• Severe bloating, abdominal pain, diarrhea, or vomiting.

Overview of Allergies

When our bodies are under attack by pathogens or other foreign particles that are perceived to be harmful, an immune response is sparked to eliminate the invaders. Our immune systems have evolved a variety of tricks to help identify these attackers and then recruit special cells to the sites of attack that can destroy them and protect the body. Once such protective response is the allergic response, though in these cases, the body is overreacting to the invasion of something harmless, sending the immune system into overdrive. Thus, allergies belong to a category of immune responses known as hypersensitivity.

Upon recognizing the allergen as an intruder, the body sends in immune cells called T helper cells. These T helper cells secrete signaling molecules that recruit other immune cells to help deal with the attacker, including B cells, which are stimulated to produce an antibody called IgE. The IgE antibodies made are specifically responsive to the allergen — they recognize it and bind it. Once antibodies are bound to the allergen, they can stimulate the production of molecules called histamines. Histamines alter the cells in the capillaries to allow white blood cells and other immune cells through so that they may eliminate the attacker. This also causes the inflammation (redness and swelling) associated with this part of the immune response, which the root of many symptoms associated with allergies.

Because the IgE molecules specific to the antigen can continue to circulate in the body, this also gives the immune system a sort of memory for what it has been exposed to. This immunological memory is the basis of many vaccines, which provide a measured exposure of a potential attacker, so that the body can very quickly respond to it if it is encountered again in life. Allergens provoke an unusually strong response, however, and why this hypersensitivity occurs in some people and not others is unclear.

Symptoms of Allergies

Allergy symptoms vary depending on where the allergen enters the body and the strength of the allergic reaction that occurs. Symptoms may include:

• Sneezing, coughing, wheezing, and constriction of the airways, sometimes accompanied by asthma.
• Swelling and inflammation of the nasal tissues and sinuses.
• Blockage, feelings of fullness, or pain within the ears.
• Redness and itchiness of the eyes (conjunctivitis).
• Rashes, eczema, or hives appearing on the skin.
• Severe bloating, abdominal pain, diarrhea, or vomiting.

Risk Factors of Allergies

If allergies are mild, they may pose little other risk beyond annoyance for the sufferer. Chronic allergies, such as seasonal allergies, may keep a person’s immune system in overdrive, however, which can be very exhausting and potentially make them more susceptible to other illnesses and infections. The immune system has limited resources, so if its response is diverted toward something inconsequential, like pollen, they may not be able to adequately fight off pathogens and other infections.

The chronic inflammation associated with allergies can be damaging to tissues, as well, increasing the possibilities of outside infection. Many chronic allergy sufferers also endure frequent sore throats, sinus infections, and skin problems.

If the allergic response very suddenly triggers a massive release of histamines into the body, the rapid permeabilization of all the blood vessels can cause a devastating drop in blood pressure and release fluids into the lungs, making it difficult to breathe. There can be swelling of the face, neck, and throat, additionally obstructing breathing, and a person may also have convulsions. This extreme hypersensitivity response, called anaphylaxis, is a whole-body allergic reaction that can be fatal if not treated immediately.

Causes of Allergies

Specifically, allergies are caused by the allergens the body encounters. Many allergens are airborne, inducing the allergic response as they come into contact with the eyes, noses, mouths, and lungs upon inhalation. Seasonal allergies are caused by pollen, and people may also develop allergies to dust, mold, insect stings, medications, and certain foods. (Please see our article on food allergies for more information.) Contact of an allergen with the skin can also potentially provoke an allergic response, as is the case with latex allergies.

More generally, the factors that predispose a person to developing allergies are less clear. There appear to be both genetic and environmental factors at play, the combination of which helps determine both the source and intensity of allergic responses. Children of parents that have allergies are more likely to develop allergies than those born to non-allergic parents, though not consistently with the same allergens. Twins are very likely to respond to the same allergens. Studies found that identical and fraternal twins shared allergy profiles 70% and 40% of the time, respectively.

Age and gender may also influence the development of allergies. Studies have shown that levels of IgE, the antibody which initiates the immune response, peak in childhood and then decline between ages ten and thirty. Overall, boys seem to have a higher incidence of allergies than girls.

Early exposure to allergens is thought by some to increase the risk of developing allergies during adulthood. Statistics suggest that allergies are more prevalent in urbanized areas than rural ones, and tend to be more of a problem in industrialized countries than developing areas of the world.

In better developed areas, the body is exposed to more pollutants and industrial byproducts, which could possibly make the body more sensitive to allergens. Overall, however, epidemiological data suggests a much lower incidence of autoimmune and immunological disorders in the developing world. This has lead to the hygiene hypothesis, which instead suggests that challenges to a young child’s immune system actually have long term benefits. By exposing the immune system to allergens and pathogens early in life, it is strengthened and also better tuned such that it will not over-respond, as in the case of the allergic response. Some proponents of this theory add that certain pathogens and parasites ingested as a part of less “clean” living conditions may also be a benefit, as they effectively reduce what might otherwise be an overzealous immune response. In other words, letting your child play in the dirt (and even eat some of it) may actually make their immune system more robust in the long term.

Conventional Treatment of Allergies

Diagnosis of specific allergies is generally done using skin tests or blood tests. In skin testing, a zone is selected on the patient’s arm or back, and small doses of common allergens, such as pollen, peanut extract, dust, or grass, will be injected in small quantities. The doctor can then examine the area surrounding the injection for inflammation, which generally occurs within the first thirty minutes. Evaluation of these responses can help the doctor generate an allergy profile for the patient. Naturally, if a severe allergy is suspected (in cases where there has been anaphylaxis, for example), a blood test can be performed instead to look for the presence of IgE specific to different allergens.

If possible, it is recommended that people with allergies make efforts to avoid their allergens. In cases where this is not possible (as with seasonal allergies), then there are many drugs available to help quell the overactive immune response. Antihistamines, for example, can disrupt the histamine response responsible for initiating many of the symptoms. Cortisone, hydrocortisone, dexamethasone, and epinephrine are also useful for suppressing the immune response during an allergic reaction. During an anaphylactic response, decongestants, anti-cholinergics, and mast cell stabilizers (which will decrease histamine release) may also be used to relieve the symptoms.

One treatment that some allergy patients elect to undergo is immunotherapy, in which they are vaccinated with progressively larger doses of the allergens that affect them. Following a skin test to determine what the patient is allergic to, the doctors can formulate a mixture of these allergens to be injected (or ingested) periodically. By repeatedly exposing the immune system to the allergens at low levels, the goal is to help desensitize the immune system, eventually reducing or eliminating the allergic reaction all together. This is a long term commitment on the part of the patient, though it has proven to be a successful in reducing hypersensitivity.