Allergies and their resultant symptoms can vary widely, depending on the nature of the allergic reaction and the organ systems involved. The symptoms from allergies can result from contact of the allergen with the skin, from breathing the allergen, or from ingesting the allergen.
Allergic symptoms in the skin that are the result of direct contact are usually limited to the skin itself, but, if severe, the allergy symptoms can be systemic and involve multiple organ systems. The classic example of allergy symptoms from direct contact with the allergen is the allergy rash from contact with poison ivy. Contact with the oil in the poison ivy plant results in a red, raised rash with intense itching. When severe, blisters can form with resultant weeping from the blister. This condition, called contact allergic dermatitis can also result from contact with latex, cleaning solutions, soaps, shampoos, and virtually any chemical which comes in contact with the skin.
Allergies can also result in urticaria, commonly called hives. Although commonly not caused by allergies, the symptoms produced by non-allergic causes are identical to those caused by allergies. As an example, a classic case of acute hives may result from a food allergy, such as a peanut allergy. The culprit, as in all allergic reactions, is histamine and other chemical mediators which are released in abnormal amounts. These chemicals cause the blood vessels in the skin to dilate, causing leaks between the cells in the blood vessels, allowing plasma to escape into the tissues. This results in red, raised hives which can measure from a few millimeters in diameter to many centimeters. They can be round or irregularly shaped, and sometimes they can resemble a target or a bulls-eye. They can appear isolated on one part of the body such as the face, or they be generalized and cover the entire body. These hives are characteristically very, very itchy.
Allergy symptoms in the skin can also occur with eczema, or atopic dermatitis. When mild, the allergy rash can appear as a faint pink or red dry patch on the skin. When the inflammation worsens, or if the skin becomes infected, the rash takes on a more angry red appearance and can ooze clear or pussy fluid. When chronic and long-lasting, the skin can become very thick, a process called lichenification. When moderately severe and wide-spread, the entire skin of the individual with eczema will be very dry. Like in almost all allergic reactions, itching is a particularly challenging allergy symptom in the skin.
Another form of allergy which results from contact is the allergy eye symptoms which results from exposure of pollen or other allergens in the eyes. This condition, called allergic conjunctivitis, is easy to diagnosis as the allergy symptoms it produces are quite classic in their presentation. Shortly after contact of the pollen with the lining of the eyes, histamine is released. The histamine and other chemicals released results in tearing, redness and swelling in the lining of the eyes, injection in the blood vessels of the eyes themselves, and moderate to severe itching. Allergy eye symptoms are commonly confused with an eye infection. Bacterial or viral conjunctivitis generally produce a thick yellow discharge and the eyes are somewhat painful. Allergy symptoms, on the other hand, generally produce a thin watery discharge. But, the one symptom that is almost always present in allergy eyes symptoms is itching, sometimes intense eye itching, usually in the inner corners of the eyes. Itching is such a universal presentation as an allergy symptom that, if absent, one may be hard pressed to cause the symptoms on allergies. It should be noted that allergens other than pollens can cause allergy eye symptoms. Allergies to pets, especially cats, can result in intense allergy eye symptoms. Other triggering allergens include dust mites and mold spores.
These allergy symptoms of the nose are familiar to most people. Allergy symptoms in the nose consist of a clear runny nose, sneezing, itching, and nasal congestion. These allergy symptoms can occur after an allergen is breathed onto the lining of the nose. The histamine released causes the mucous glands in the nose to produce copious amounts of mucous, resulting in severe runny nose and post nasal drip. The histamine also causes erectile tissue to swell. The structures in the nose that swell are called turbinates. When the turbinates swell, it leads to nasal congestion, either on one side of the nose, or both.
Upon inhalation of allergens in the bronchial tubes, lung allergy symptoms can occur in susceptible individuals. The allergy symptoms which are produced are dependent on the structures in the lungs that are affected. For example, an inhaled allergen can result in tightening of the smooth muscles which surround the bronchial tubes. This leads to wheezing, tightness in the chest, and sometimes difficulty breathing. Wheezing is a high pitched squeaking sound which is generally only heard with a stethoscope, but it sometimes can be audible without the aid of a stethoscope. It is most commonly heard on expiration (breathing out), but can also be heard during inspiration (breathing in).
Allergies will also cause symptoms in the lungs when swelling and mucous production occurs as a result of allergic inflammation. The diameter of the bronchial tubes through which air flows will then be compromised. Subsequent asthma symptoms can include wheezing, a sensation of tightness in the chest, and difficulty breathing. In babies and young children, it is not uncommon to see retractions of the chest wall during forced inspiration due to labored breathing.
Coughing is probably the most common asthma symptom, especially in children. This is due to the increased sensitivity which occurs with even mild inflammation in the bronchial tubes. The cough receptors become highly sensitive and can be stimulated by minor triggers. Coughing can be the only presenting symptom of asthma. As a matter of fact, asthma is one of the most common causes of a recurrent or chronic coughing in both children and adults.
Symptoms of allergies in the gastrointestinal tract are somewhat age dependent. For example, in babies, allergy symptoms to a food might present as recurrent spitting or projectile vomiting after eating, colic or irritability, diarrhea which can be bloody, abdominal pain, and even failure to thrive.
Older children will often complain of recurrent or chronic abdominal discomfort, bloating, loose stools or diarrhea, constipation, and signs of reflux. Symptoms of reflux which can be on an allergic basis might include burping, chest burning or chest pain, and other classic signs of indigestion.