TYPES OF ALLERGIES

Cat Allergies

Life with cat allergies -- whether they're yours or a family member's -- can raise a lot of questions. Could a cat allergy explain your son's never-ending cold symptoms? Will you regret giving in to your daughter's demands for a kitten, despite your allergies? Will a so-called hypoallergenic cat allow you to have the pet you've always wanted without making you a sneezing, sniffling mess?

Here are some answers -- what you need to know about cat allergies, from causes to treatments.

Signs and symptoms

Many allergens such as dust or pollen are airborne particles. In these cases, symptoms arise in areas in contact with air, such as eyes, nose, and lungs. For instance, allergic rhinitis, also known as hay fever, causes irritation of the nose, sneezing, itching, and redness of the eyes.^[3] 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.^[4]

Aside from these ambient allergens, allergic reactions can result from foods, insect stings, and reactions to medications like aspirin and antibiotics such as penicillin. Symptoms of food allergy include abdominal pain, bloating, vomiting, diarrhea, itchy skin, and swelling of the skin during hives. Food allergies rarely cause respiratory (asthmatic) reactions, or rhinitis.^[5] 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.^[6][7][8] Depending on 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. The severity of this type of allergic response often requires injections of epinephrine, sometimes through a device known as the EpiPen or Twinject auto-injector. The nature of anaphylaxis is such that the reaction can seem to be subsiding, but may recur throughout a prolonged period of time.^[8]

Substances that come into contact with the skin, such as latex, are also common causes of allergic reactions, known as contact dermatitis or eczema.^[9] 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.^[10]

Cause

Risk factors for allergy can be placed in two general categories, namely host and environmental factors.^[11] Host factors include heredity, gender, race, and age, with heredity being by far the most significant. However, there have been recent increases in the incidence of allergic disorders that cannot be explained by genetic factors alone. Four major environmental candidates are alterations in exposure to infectious diseases during early childhood, environmental pollution, allergen levels, and dietary changes.^[12]

Foods

One of the most common food allergies is a sensitivity to peanuts. Peanut allergies may be extremely severe, but can sometimes be outgrown by children school-age.^[13] Tree nuts, including pecans, pistachios, pine nuts, and walnuts, are another common allergen. Sufferers may be sensitive to one, or many, tree nuts.^[14] Also seeds, including sesame seeds and poppy seeds, contain oils where protein is present, which may elicit an allergic reaction.^[14]

Egg allergies affect one to two percent of children but are outgrown by about two-thirds of children by the age of 5.^[15] The sensitivity is usually to proteins in the white rather than the yolk.^[14]

Milk, from cows, goats, or sheep, is another common allergy-causing food, and many sufferers are also unable to tolerate dairy products such as cheese. Lactose intolerance, a common reaction to milk, is not in fact a form of allergy. A small portion of children with a milk allergy, roughly ten percent, will have a reaction to beef. Beef contains a small amount of protein that is present in cow's milk.^[16]

Other foods containing allergenic proteins include soy, wheat, maize, fish, shellfish, fruits, vegetables, spices, synthetic and natural colors, chicken, and chemical additives.^{[citation needed]}

Non-food proteins

Latex can trigger an IgE-mediated cutaneous, respiratory, and systemic reaction. The prevalence of latex allergy in the general population is believed to be less than one percent. In a hospital study, one in 800 surgical patients (0.125 percent) report latex sensitivity, although the sensitivity among healthcare workers is higher, between seven and ten percent. Researchers attribute this higher level to the exposure of healthcare workers to areas with significant airborne latex allergens, such as operating rooms, intensive-care units, and dental suites. These latex-rich environments may sensitize healthcare workers who regularly inhale allergenic proteins.^[17]

The most prevalent response to latex is an allergic contact dermatitis, a delayed hypersensitive reaction appearing as dry, crusted lesions. This reaction usually lasts 48 to 96 hours. Sweating or rubbing the area under the glove aggravates the lesions, possibly leading to ulcerations.^[17] Anaphylactic reactions occur most often in sensitive patients, who have been exposed to the surgeon's latex gloves during abdominal surgery, but other mucosal exposures, such as dental procedures, can also produce systemic reactions.^[17]

Latex and banana sensitivity may cross-react; furthermore, patients with latex allergy may also have sensitivities to avocado, kiwifruit, and chestnut.^[18] These patients often have perioral itching and local urticaria. Only occasionally have these food-induced allergies induced systemic responses. Researchers suspect that the cross-reactivity of latex with banana, avocado, kiwifruit, and chestnut occurs because latex proteins are structurally homologous with some plant proteins.^[17]

Toxins interacting with proteins

Another non-food protein reaction, urushiol-induced contact dermatitis, originates after contact with poison ivy, eastern poison oak, western poison oak, or poison sumac. Urushiol, which is not itself a protein, acts as a hapten and chemically reacts with, binds to, and changes the shape of integral membrane proteins on exposed skin cells. The immune system does not recognize the affected cells as normal parts of the body, causing a T-cell-mediated

Skin testing for allergies is used to identify the substances that are causing your allergy symptoms. It is often performed by applying an extract of an allergen to your skin, scratching or pricking the skin to allow exposure, and then evaluating the skin's reaction. It may also be done by injecting the allergen under the skin, or by applying it to a patch that is worn on the skin for a specified period of time.