Allergy - Simple or complicated?

Allergy is a disorder of the immune system often also referred to as atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid.

Mild allergies like hay fever are highly prevalent in the human population and cause symptoms such as allergic conjunctivitis, itchiness, and runny nose.

A variety of tests now exist to diagnose allergic conditions; these include testing the skin for responses to known allergens or analyzing the blood for the presence and levels of allergen-specific IgE.  That’s the major breakthrough in understanding the mechanisms of allergy which was the discovery of the antibody class labeled immunoglobulin E (IgE). Kimishige Ishizaka and his co-workers were the first to isolate and describe IgE in the 1960s

Many allergens such as dust or pollen are airborne particles.  Inhaled allergens can also lead to asthmatic symptoms, caused by narrowing of the airways (bronchoconstriction) and increased production of mucus in the lungs, shortness of breath (dyspnea), coughing and wheezing.

Aside from these ambient allergens, allergic reactions can result from foods, insect stings, and reactions to medications like aspirin and antibiotics such as penicillin.

Insect stings, antibiotics, and certain medicines produce a systemic allergic response that is also called anaphylaxis; multiple organ systems can be affected, including the digestive system, the respiratory system, and the circulatory system.

Depending of the rate of severity, it can cause cutaneous reactions, bronchoconstriction, edema, hypotension, coma, and even death. This type of reaction can be triggered suddenly, or the onset can be delayed. Substances that come into contact with the skin, such as latex, are also common causes of allergic reactions, known as contact dermatitis or eczema.

Skin allergies frequently cause rashes, or swelling and inflammation within the skin, in what is known as a “wheal and flare” reaction characteristic of hives and angioedema.

Risk factors for allergy can be placed in two general categories, namely host and environmental factors. Host factors include heredity, sex, race, and age, with heredity being by far the most significant.

Allergic diseases are strongly familial, identical twins are likely to have the same allergic diseases about 70% of the time; the same allergy occurs about 40% of the time in non-identical twins.

Some allergies, however, are not consistent along genealogies; parents who are allergic to peanuts may have children who are allergic to ragweed.

The risk of allergic sensitization and the development of allergies vary with age, with young children most at risk.

Several studies have shown that IgE levels are highest in childhood and fall rapidly between the ages of 10 and 30 years.

The peak prevalence of hay fever is highest in children and young adults and the incidence of asthma is highest in children under 10.

Ethnicity may play a role in some allergies, however racial factors have been difficult to separate from environmental influences and changes due to migration.

Interestingly, it has been suggested that different genetic loci are responsible for asthma, specifically, in people of Caucasian, Hispanic, Asian, and African origins.

According to the hygiene hypothesis, proposed by David P. Strachan, allergic diseases are caused by inappropriate immunological responses to harmless antigens driven by a TH2-mediated immune response.

In other words, individuals living in too sterile an environment are not exposed to enough pathogens to keep the immune system busy.

The hygiene hypothesis was developed to explain the observation that hay fever and eczema, both allergic diseases, were less common in children from larger families, which were presumably exposed to more infectious agents through their siblings, than in children from families with only one child. The hygiene hypothesis has been extensively investigated by immunologists and epidemiologists and has become an important theoretical framework for the study of allergic disorders.

Epidemiological data supports the hygiene hypothesis.

The use of antibiotics in the first year of life has been linked to asthma and other allergic diseases.

The use of antibacterial cleaning products has also been associated with higher incidence of asthma, as has birth by Caesarean section rather than vaginal birth.

International differences have been associated with the number of individuals within a population that suffer from allergy.

Exposure to allergens, especially in early life, is an important risk factor for allergy.

For assessing the presence of allergen-specific IgE antibodies, allergy skin testing is preferred over blood allergy tests because it is more sensitive and specific, simpler to use, and less expensive.

Skin testing is also known as “puncture testing” and “prick testing” due to the series of tiny puncture or pricks made into the patient’s skin. Small amounts of suspected allergens and/or their extracts (pollen, grass, mite proteins, peanut extract, etc.) are introduced to sites on the skin marked with pen or dye (the ink/dye should be carefully selected, lest it cause an allergic response itself).

Some patients may believe they have determined their own allergic sensitivity from observation, but a skin test has been shown to be much better than patient observation to detect allergy.

If a serious life threatening anaphylactic reaction has brought a patient in for evaluation, some allergists will prefer an initial blood test prior to performing the skin prick test.

Various blood allergy testing methods are also available for detecting allergy to specific substances. This kind of testing measures a “total IgE level” - an estimate of IgE contained within the patient’s serum.

There have been enormous improvements in the medical treatments used to treat allergic conditions.

Traditionally treatment and management of allergies involved simply avoiding the allergen in question or otherwise reducing exposure. For instance, people with cat allergies were encouraged to avoid them.

If you have indoor allergies, your allergy symptoms are likely caused by dust mite allergens, mold allergens and pet dander. While it may be easy to understand how molds and pets contribute to allergy symptoms, dust and dust mite allergens may be more difficult.

What are Dust Mites?

Dust mites are eight-legged arachnids and are relatives of spiders and ticks. The dust mite is microscopic and, unlike bed bugs, cannot be seen by the human eye.

Allergies are not caused by the dust mite being inhaled, but instead, allergy symptoms stem from a combination of waste particles from dust mites as well as their dead body fragments.

Where do Dust Mites Live in the Home?

Dust mites can live in even the cleanest homes and are present in nearly all homes in areas where the relative humidity is greater than 50% for some portion of the year. Dust mites are photophobic, which means that they thrive in dark, warm and humid environments.

While it is impossible to eliminate dust mites altogether, you can minimize your exposure to dust mite allergens and find allergy relief.

Don’t despair over not being able to completely eliminate dust mites, as scientific studies have shown that taking allergen avoidance steps to minimize dust mite allergen exposure in the bedroom leads to a decrease in allergic symptoms and a decrease in medication requirements for people with dust mite allergies.

Use allergy encasings to create a barrier between you and the allergens in the bed. Wash linens, blankets and any un-encased bedding every week in hot water.