Allergy

What is Allergy?

Allergies are a wide-ranging topic that involves the body’s immune system reacting to foreign substances usually found in our surroundings, leading to a reaction known as hypersensitivity. Hypersensitivity is when the immune system overreacts to common substances that are usually not harmful. This overreaction can result in minor conditions such as atopic dermatitis (skin inflammation) and rhinitis (runny or stuffy nose), or in severe conditions such as anaphylaxis, anaphylactoid reactions, and asthma. In this context, we will focus on anaphylaxis. It’s important to note that atopic dermatitis and allergic asthma share many characteristics and treatments with anaphylaxis.

Anaphylaxis is most commonly triggered by foods, medications, insect stings, and allergen immunotherapies, which are treatments for allergies. Any substance that triggers the release of certain substances from mast cells or basophils, two types of cells in the immune system, can cause anaphylaxis. The exact definition of what constitutes an allergy and anaphylaxis has changed over time. In 2005, a group of clinical experts came together to better identify and set up criteria for diagnosing anaphylaxis. It’s estimated that anaphylaxis affects between 0.5 and 2% of the people at any given time, and this rate has been going up. Over a lifetime, it’s estimated that about 1.6% of the population will experience anaphylaxis.

What Causes Allergy?

Anaphylaxis is a severe allergic reaction that can happen very quickly, usually within minutes to hours. It happens when your immune system overreacts to harmful substances, called allergens. This reaction involves specific immune system cells known as mast cells and basophils which release ‘histamine’ and other substances that cause your body to react in many ways. This reaction can tighten your airways, increase blood flow in your skin and cause your face to become red.

Well-known triggers of anaphylaxis include bee stings, peanuts, latex and some types of medication, but there are also other substances that can trigger this reaction. To understand if a person has had an anaphylaxis reaction, doctors look for:

1. Quick onset of symptoms involving your skin or the moist lining of your mouth. This could mean hives, itching, becoming red in the face, or swelling of the lips, tongue, or throat. Along with these symptoms, one or both of the following should also be present:
a) Difficulty breathing, wheezing, narrowing of the airways, abnormal sounds when breathing, and lower levels of oxygen.
b) Lower blood pressure and signs or symptoms of not getting enough blood to the body’s organs.

2. Two or more symptoms that happen quickly after exposure to a substance the patient is likely to be allergic to:
a) Skin symptoms such as hives, itching or flushing, or swollen lips, tongue or throat.
b) Trouble breathing caused by swelling, wheezing, or narrowing of the airways.
c) Lower blood pressure or other symptoms such as fainting.
d) Persistent stomach symptoms such as cramping and vomiting.

3. Lower blood pressure alone after exposure to a known allergen (a substance known to cause an allergic reaction).

It’s important to note that in some cases, skin symptoms may not be present or they may not be noticed. In these situations, doctors will check for other symptoms like stomach problems or other listed symptoms to identify anaphylaxis.

Also, if a patient is found to have lower than normal blood pressure after exposure to a substance they’re known to be allergic to, it could be considered as anaphylaxis. For adults, it’s defined as a systolic blood pressure less than 90 or more than 30 percent lower than their usual readings. For children, it’s a blood pressure reading lower than normal for their age.

Finally, if a person’s anaphylaxis symptoms improve with a medicine called epinephrine, they likely had an anaphylactic reaction.

Risk Factors and Frequency for Allergy

Anaphylaxis, which is a severe allergic reaction, affects 0.5 to 2 percent of people in developed countries, and rates are increasing. In the United States, around 1.6 percent of people will experience anaphylaxis in their lifetime. Allergic atopic dermatitis, a type of skin condition, is quite common, affecting 5 to 20 percent of kids worldwide. In the United States, this figure stands at 11 percent.

Allergic rhinitis, or hay fever, has a prevalence of 10 to 30 percent in the United States. Rhinoconjunctivitis, an inflammation of the nose and eyes, was found to affect 8.5 percent of 6 to 7-year-old kids, and 14.6 percent of 13 to 14-year-old kids in a study of Asthma and Allergies in children. The study also found that these types of allergies are becoming more widespread in developed countries.

Atopy is the tendency to have severe allergic reactions due to a genetic predisposition. It means that the body produces a substance called IgE in response to exposure to allergens. This could be linked to the increase in the number of allergic conditions observed.

Signs and Symptoms of Allergy

Anaphylaxis is a severe allergic reaction often involving multiple body systems. It usually starts with a rash or swelling of the lips or tongue, and can even lead to collapse. Understanding a patient’s recent activities is crucial in determining what might have triggered the reaction. However, the cause of the symptoms isn’t always immediately apparent, and information from other people who were nearby can be helpful. Anaphylaxis should be considered in patients who present with any of the following symptoms that progressively worsen:

• Skin: itchiness, visible flushing, hives
• Mucosa: swelling of lips, tongue, eyes, feeling of a full throat or difficulty swallowing
• Lung/respiratory: tightness in the chest, shortness of breath, wheezing, hoarse voice, noisy breathing, runny nose
• Gastrointestinal: spasms in the chest with nausea and retching, vomiting, abdominal cramping, diarrhea
• Cardiovascular: rapid heart rate paired with above symptoms, fainting, collapse, low blood pressure, chest pain, heart palpitations
• Central nervous system: disturbed rhythm, altered mental state, feeling of impending doom, seizures, headache
• Ocular: itching around the eyes, redness and swelling, tearing up, red eyes
• Urinary or sexual organs: bladder cramping, uterine cramps

Children experiencing anaphylaxis may become unusually clingy, cry more than usual, seem irritable or stop playing. Some might show noisy breathing indicating an issue with the throat. Patients might share that symptoms went away after taking over-the-counter antihistamines only to return. It’s important to note that anaphylaxis can still occur even without a known prior exposure to the trigger. Also, some medications can trigger anaphylaxis even if they haven’t caused a reaction in the past.

Anaphylaxis can sometimes relapse, where symptoms disappear and then return even without further exposure to the trigger – this is known as biphasic anaphylaxis. The reaction can also last for hours, days or even weeks. Delayed reactions are also possible, where symptoms don’t appear until hours after exposure. It’s critical to keep the patient under observation for 4 to 6 hours after the episode to assess the cause, carry out a physical examination, determine the prognosis and the necessary patient education.

Testing for Allergy

Anaphylaxis is a condition that is diagnosed based on symptoms that a person is experiencing. Specific chemical measurements, although not readily at hand for the doctor, can confirm the allergic reaction. Certain cells in your blood, such as mast cells and basophil (a type of white blood cell), can be useful indicators if tested soon after the beginning of symptoms.

Some medical professionals suggest taking a blood test to measure levels of a chemical known as tryptase at 15 minutes, 3 hours, 6 hours, and 24 hours after the onset of symptoms. If an elevated level of tryptase is found 24 hours after symptoms start, it might indicate a need for a specialist in allergies and the immune system. This is because there could be the presence of systemic mastocytosis (a disorder common in your mast cells, a type of blood cell) or mast cell activation syndrome. Patients with these disorders can experience low blood pressure reactions to insect stings, even without any allergy linked to an antibody called immunoglobulin E (IgE). It’s also noteworthy for doctors that if your tryptase levels are high, there is a good chance you are experiencing anaphylaxis, especially if you also have low blood pressure.

Another chemical to consider is plasma histamine. Its levels peak within 5 to 15 minutes from the time symptoms start, but then rapidly decrease to normal levels within 60 minutes due to its quick breakdown by specific enzymes. However, most patients arrive at the hospital beyond this 15 to 60 minutes window so they might not find it useful to measure histamine levels since they will have returned to normal. A 24-hour urine histamine collection (taken as soon as possible after the onset of anaphylaxis) may be helpful in some cases. It will be interesting to follow new tests aiming to focus on two specific types of tryptase (mature beta-tryptase and alpha tryptase) over the amount of overall tryptase present.

Treatment Options for Allergy

Patients may experience periods of mild symptoms of an allergic reaction that spontaneously get better. However, usually, these symptoms increase in seriousness. It’s impossible to predict how severe the reaction will be, or whether it might suddenly return after appearing to go away, known as a biphasic reaction. This return of symptoms occurs in up to 15 percent of children. Some reactions continue for days or even weeks, and can occur hours after exposure. If left untreated, these instances can potentially be fatal.

Patients with certain health conditions like asthma, chronic obstructive lung disease (COPD), a disease of the lungs that blocks airflow, and interstitial lung disease which affects the space and tissue within the lung, may experience slower reactions due to prescribed antihistamines and steroids. Similarly, heart patients, and those with high blood pressure who are on medication that blocks natural body mechanisms (alpha-blockers,  beta-blockers, and ACE inhibitors) may require larger doses of epinephrine, a hormone that narrows blood vessels and opens airways to treat the reaction. 

When treating an allergic reaction, the first step is stopping contact with the allergen. This could mean decontaminating the person if they’ve been in contact with a topical agent or contaminated clothing. Proper precautions must be taken to prevent health providers from unintentionally causing an allergic reaction. Next, doctors focus on the basics, the ABC’s of emergency care i.e., checking airway, breathing, and circulation. Patients should be given oxygen and intravenous administration of fluids. The patient should also receive an intramuscular shot (directly into the muscle) of adrenaline (a shot of epinephrine), which is a fast-acting treatment for severe allergic reactions.

Depending on the severity of the person’s symptoms, this dose may need to be repeated every 5 to 15 minutes until the patient starts to show signs of improvement. In some severe cases, patients are prescribed medication to stop vomiting (antiemetics), given antihistamines, and also administered a medicine called glucocorticoid which helps reduce inflammation in the body.

Weight-based doses are recommended for children, using an appropriate calculation to determine the right amount of medication.

Aerosolized albuterol, a medication to help with breathing, can be used for wheezing and spasms of the bronchial muscles. For patients who do not respond to intravenous adrenaline, they may be given methylene blue, a medication that could help blood pressure by inhibiting certain body processes. Additionally, vasopressin, a hormone, and equipment to support heart and lung function (extracorporeal membrane oxygenation) may be used in very severe cases.

What else can Allergy be?

Anaphylaxis is a severe allergic reaction that can be complex to diagnose because it presents differently in different people. Various other conditions could look like anaphylaxis, depending on the symptoms.

Situations when a person faints and has a heart rhythm disorder or a seizure along with a loss of bladder or bowel control could be mistaken for anaphylaxis. Other possibilities when a person has low blood pressure might include a heart attack, sepsis, and other conditions that cause a sudden drop in blood pressure. The breathing difficulties that result from anaphylaxis can be mimicked by conditions like epiglottitis, croup, laryngeal spasms, swellings in the throat such as angioedema, and obstructions in the airway or esophagus. Furthermore, certain gastrointestinal conditions, and even certain drug reactions can seem like anaphylaxis because of the release of certain chemicals in the body.

Diagnosing anaphylaxis is mostly based on the symptoms observed. Although explicit testing can confirm or rule out other causes, it should not hold back treatment if anaphylaxis is suspected. A test for a chemical called tryptase is sometimes recommended, but this is often not available in emergency departments. Moreover, a normal level of tryptase does not necessarily rule out anaphylaxis because it can be elevated in conditions like mastocytosis and in children.

Other tests are being developed, but they aren’t widely available yet. These include tests for chemicals such as beta tryptase and histamines.

Doctors should think about anaphylaxis as a potential diagnosis if:

• There is unexplained low blood pressure, especially in patients who are not low on bodily fluids. The patient’s baseline blood pressure should be factored in.
• There are unexplained causes of breathing difficulties, skin symptoms, or gastrointestinal symptoms (note that about 20 percent of patients do not show all the typical symptoms).
• The person’s history suggests symptoms of itching, flushing, hives, and difficulty breathing before they visited the hospital.
• The person has had certain reactions in the past known as anaphylactoid reactions, which occur due to the release of certain chemicals from immune cells. These reactions can be triggered by things like contrast media (used in certain medical scans), exposure to cold, and physical activity.

Furthermore, some seemingly harmless foods can contain ingredients that can cause anaphylaxis in allergic individuals. This can include popsicles containing legume extracts, which can be an issue for those with peanut or legume allergies. A comprehensive review of all activities and food consumed in the 24 hours before the symptoms started is very important.

Speaking with patients with psychiatric conditions may require more time to get all the necessary information. Special populations such as pregnant, low-income, homeless, and elderly people may be specifically susceptible to problems if there’s a delay in diagnosis.

What to expect with Allergy

Patients may see mild symptoms naturally clear up on their own. Unfortunately, the severity of symptoms typically increase over time. It’s hard to predict how severe the symptoms will become, as this can be influenced by various factors. Certain individuals can also experience what’s known as ‘biphasic reactions’—a return of symptoms after they seemed to have disappeared, even though they have not come in contact with the particular allergen again. This happens in about 15 percent of children and 21 percent overall. The reaction can also drag on for days, or even weeks in some cases. In other situations, overly sensitive reactions to allergens can develop into anaphylaxis, a severe allergic reaction, hours after exposure. If not treated, this can be potentially life-threatening.

Certain conditions may make a person more likely to have severe outcomes, such as asthma, chronic obstructive pulmonary disease, and a condition known as interstitial lung disease. These patients may have delayed reactions if they have taken certain treatments like antihistamines (drugs that treat allergies) and steroids. Likewise, those with heart disease and high blood pressure, who are taking specific medications like alpha-blockers, beta-blockers, and ACE inhibitors, might need larger doses of epinephrine–a drug used to treat severe allergic reactions or anaphylaxis.

Possible Complications When Diagnosed with Allergy

Anaphylaxis is a severe allergic reaction that can be deadly if it isn’t identified and treated immediately. A study that looked at 164 cases of anaphylaxis that resulted in death found that the average time between the start of symptoms and the individual experiencing heart or respiratory failure was around 5 minutes. This was particularly true if the anaphylaxis was caused by a medical procedure, rather than a food allergy or insect sting. Symptoms from food-induced anaphylaxis usually start within 30 minutes, and symptoms from insect stings often start within 15 minutes.

Failure to promptly recognize and treat anaphylaxis with adrenaline (epinephrine) can cause serious heart, circulatory, and breathing problems. Even those with pre-existing conditions like heart disease who may have a higher risk of side effects from the treatment should still receive it. That’s because the chances of anaphylaxis causing a harmful reaction are just as high. Being prepared for potential complications from their other health conditions is a key part of managing these cases.

If heart damage happens as a result of the adrenaline used to treat anaphylaxis, the patient will have to receive further treatment for their heart condition and potentially see a heart specialist. Additionally, people with severe asthma or chronic obstructive pulmonary disease (COPD) may need additional treatment to make sure they can breathe properly.

• Severe allergic reactions
• Symptoms often start in 5 minutes
• Anticipate and treat complications from other health conditions
• If damage to the heart occurs, further treatment and seeing a heart specialist may be necessary
• People with severe asthma or COPD may need additional treatment to ensure they can breathe properly

Preventing Allergy

Patients should be educated about the serious allergic reaction called anaphylaxis, and the treatment required if it happens again. If the trigger or allergen causing this intense reaction is identified, the patient will be informed and advised to prevent future interactions with it.

Patients should also be guided on how to use an EpiPen, a device which can inject a dose of medicine called epinephrine, that can help combat allergic reactions swiftly. They should understand that after using the EpiPen, they should head straight to the emergency department.

Beside this, it’s crucial for patients to recognize the early signs of anaphylaxis which can include itching, skin redness, hives, or a runny nose. More advanced symptoms can involve trouble breathing, wheezing, vomiting, swelling of the throat and esophagus, diarrhea, and feeling dizzy to the point of passing out.

If additional assessment and treatment are needed, patients can be referred to a specialist in one’s immune system and allergies, also known as an allergist/immunologist. Patients who are highly allergic to certain food substances like peanuts or legumes should be educated on how to read food labels to avoid accidental exposure.

Patients who have severe reactions should consider wearing allergy bracelets and having rescue kits on hand. These kits often contain an EpiPen and either an oral or injectable antihistamine, a medication that can help reduce allergy symptoms.