Allergy Testing

Allergies are so common in the U.S. that they are often seen as little more than a nuisance. However, allergic reactions can occasionally escalate to medical emergencies, which is why it’s important to discuss suspected allergies with the family doctor. Allergies can manifest in people of any age, sex or race, and there are few clear patterns as to how they initially present. In other words, a child may develop allergies at a young age, seemingly grow out of them in time, only to have them return later in adult life. And, of course, many people never grow out of their allergies and must be constantly vigilant about their environment.

There are diagnostic and treatment options, though, for people who believe they are suffering from allergies. Diagnostic testing is safe and done in a controlled environment, and treatment can control and possibly even eliminate some frustrating symptoms.

What is an allergy?

First, a quick look into what an allergy actually is. One of the marvels of the human body is its incredible ability to fight off all kinds of invaders. But like with any complex biological system, it doesn’t always work perfectly.

Allergies represent benign foreign particles that, for some reason, produce medical symptoms in some people. The biological mechanisms involved in an allergic reaction are highly involved. Simply put, when the body’s immune cells detect the allergen, it begins a cascading signaling effect that results in the kind of response to any other invader. In effect, the immune system can’t tell the difference between the allergen and something truly dangerous.

Allergens come in many forms. They may include tree or ragweed pollen, cockroaches, latex, pet dander and many types of food, among others. A single allergy test may study upwards of 40 or 50 samples, so allergens can come from just about anywhere.

Why do people develop allergies?

Although allergies have been studied for decades and decades, the picture is still incomplete. There are some factors that are clearly recognized. Sex, race and age all play a part, but their roles are minor compared to heredity. Inherited immune system characteristics appear to play a large part in the development of allergies. Parents that possess allergies are more likely to have children with allergies, and this relationship is profound between twins. Non-identical twins have a 40 percent likelihood of sharing the same allergic reactions. Identical twins have about a 70 percent chance of presenting with the same allergies. Heredity is clearly a factor.

However, family genealogies that are affected by allergies often do not show a consistent pattern in what allergies are present. In other words, a parent that has an allergy to tree pollen may be more likely to have a child that is allergic to something, but the chance of that child developing an allergy to tree pollen as well is no higher than developing an allergy to anything else. This, perhaps, means that parents are passing on an overactive immune system to their children, but it’s the environment that determines what, specifically, the child’s allergies will be.

There is an emerging idea among allergists known as the hygiene hypothesis. According to the hypothesis, it is crucial for infants, toddlers and children to be exposed to some bacteria and viruses to effectively calibrate their immune system. It’s a compelling hypothesis because the prevalence of allergic conditions has steadily increased since the industrial revolution and the implementation of better sanitary standards.

Perhaps the most interesting pieces of evidence that support the hypothesis are the increased risk of asthma in children exposed to antibacterial cleaning products, and the increased risk of asthma in children who were given antibiotics during their first year of life. There are studies that back these conclusions, but it is important to point out that the hygiene hypothesis is still just a hypothesis, and should not be interpreted by parents to intentionally expose their children to pathogens. Most children will build the immune system they need in a normal home environment.

What are some complications associated with allergic reactions?

Allergic conditions can range from an infrequent annoyance to a life-threatening, chronic condition. Some of the most common complications arising from allergen exposure include:

  1. Rhinitis – Rhinitis is what most people think of when they think of allergens. About 10 percent of all people in the U.S. suffer from occasional rhinitis, and it ranges in severity. Rhinitis refers to any allergic symptoms in the nose and its mucous membranes, and those usually include a runny or stuffy nose, nasal drip and sneezing. In some cases, the eyes may also be affected, and will present with redness, watering and itchiness. Almost all instances of allergic rhinitis are due to airborne allergens, with pollen and dander chief among them. Rhinitis is rarely serious, but it can affect a person’s quality of life if symptoms are persistent and creating painful irritation.
  2. Contact dermatitis – Contact dermatitis is the medical term for skin allergies. Contact dermatitis is unlike other allergic reactions in that there is a lag between when the allergy contacts the skin and when symptoms present. In some instances, it may take days for symptoms to develop after exposure to the allergen. Symptoms of contact dermatitis include a clearly visible rash, redness and itchiness. In some cases, blisters, welts or hives may also be present. Some common allergic triggers involving contact dermatitis include certain plants, chemicals, animal dander, medicines or insect stings.
  3. Asthma – Asthma can be caused by a variety of environmental and genetic factors, but allergic asthma is one of the most common. Close to three percent of the U.S. population suffers from allergic asthma, though there is an enormous variance in severity. For some people, symptoms only emerge once or twice a week, while others have to combat symptoms several times a day. In some, the symptoms are relatively mild and can be managed with medication or an inhaler, while others may be unable to speak and are at risk of death during an episode. Symptoms of asthma include wheezing, coughing, tightness in the chest and shortness of breath, all of which is caused by inflammation and spasms in the bronchi.
  4. Anaphylaxis – Anaphylaxis is a rare, though extremely severe variety of allergic reaction. It can be caused by nearly any type of allergen, but medication, peanuts or insect stings are usually the trigger. Anaphylaxis affects the entire body at once, dropping blood pressure to dangerous levels, swelling the throat or tongue to the point where breathing may be impossible, producing a widespread rash or producing severe gastrointestinal symptoms. Multiple symptoms usually present at once and onset is typically extremely fast. Worse, they progress quickly as well, which means anaphylaxis can be fatal within minutes. People at risk of anaphylaxis often carry an epinephrine autoinjector that can reduce the severity of symptoms, at least temporarily. This can provide enough time to get the patient to an emergency room.

The way the body responds to allergens may change or develop over time, so even if an allergic condition appears to be mild, it’s still worth getting checked out, in case it worsens with time.

Getting the Full Allergy Picture

There are numerous treatment methods available for allergies. Medications like antihistamines and various steroids can help mediate the allergic response and suppress symptoms. Immunotherapy is another option and involves exposing the patient to greater and greater concentrations of the allergen in the hopes that the body will adjust to it and better control its response. Immunotherapy is only indicated in patients suffering from rhinitis or asthma, and its use in patients with food allergies is not recommended.

But before a patient begins treatment, they need to know what allergic triggers are present. Fortunately, physicians have several diagnostic tools at their disposal in this regard. A few allergy diagnostic methods include:

1. Skin prick test – This is the frontline choice for people with mild to moderate allergies. Patients likely to suffer from anaphylaxis or severe asthma are typically steered toward a blood test instead, as it is safer.

During a skin prick test, many small samples of possible allergens are loaded on needles known as lancets. Each lancet just barely penetrates the skin, and the skin is observed for any possible reaction. If the skin becomes inflamed, then an allergen has likely been identified. Physicians also use some control samples to determine whether or not the skin is particularly sensitive or insensitive to the test, in order to eliminate the possibility of false positives or negatives. Some allergens, like insect venom, are injected deeper into the dermis.

2. Skin patch test – Skin patch tests are ordered when contact dermatitis is suspected. During the patch test, up to 30 or more patches, each loaded with a potential allergen, are placed on the back or arm. They are left in place for 48 hours to allow time for the skin to respond. During this time, the patient should not shower or engage in any activity that is likely to produce a lot of sweat. At the end of the 48 hours, the patches are removed and the skin’s condition is noted by the physician.

3. Blood testing – Blood testing is safe and quick. In general, blood testing is much easier on the body and is therefore indicated in very young or very old patients. This is because the patient is not exposed to any allergens during the test.

The patient’s blood sample is sent to a laboratory where technicians measure the concentration of lgE antibodies in the blood. The technician quantifies several varieties of the antibody to determine which allergens are likely to result in symptoms. In general, the greater the concentration of a particular lgE antibody, the greater the likelihood of developing allergic symptoms. Blood testing can also predict what allergies a patient is likely to develop with time, even if current lgE levels aren’t enough to provoke a response.

Much progress has been made in spotting and treating allergic conditions in recent decades. Now, general practitioners can perform the tests and prescribe effective treatment to their patients. With so many tools available to tackle allergies, there’s no reason not to get them checked out.