Allergic Reactions: Stroke-Like Symptoms Explained

Allergic reactions can range from mild to life-threatening, and in rare cases, they can present stroke-like symptoms. Anaphylaxis, a severe allergic reaction, can cause hypotension and circulatory dysfunction, which in turn can lead to ischemic strokes. Additionally, insect stings, particularly from honeybees, can induce anaphylactic shock and directly cause hemorrhagic and ischemic strokes due to the toxins in their venom. While it is important to be aware of the potential for allergic reactions to mimic stroke symptoms, it is crucial to remember that both conditions require immediate medical attention.

Anaphylaxis and hypotension

Anaphylaxis is a severe and potentially life-threatening allergic reaction. It can be caused by exposure or ingestion of an allergen, such as certain foods, insect stings, medications, or latex. During anaphylaxis, the immune system releases a flood of chemicals, causing a range of symptoms that can affect multiple body systems, including the skin, heart, stomach, and airways.

One of the most dangerous aspects of anaphylaxis is hypotension, or low blood pressure. This can lead to anaphylactic shock, a life-threatening condition where the body goes into shock due to extremely low blood pressure. During anaphylactic shock, the airways narrow, blocking breathing, and blood pressure drops suddenly. It can cause a sudden drop in blood pressure, blockage of airways, and even cardiac or respiratory arrest.

The symptoms of anaphylaxis usually occur within minutes of exposure to an allergen but can sometimes emerge hours later. Some people may experience a mild form of anaphylaxis, known as stage one, with symptoms such as skin rash, redness, itching, or hives. However, it can quickly progress to more severe stages, with symptoms such as difficulty breathing, extensive swelling, weak pulse, dizziness, and confusion.

The treatment for anaphylaxis is an injection of epinephrine, followed by a trip to the emergency room. Epinephrine is a form of adrenaline that works to stop the immune response to the allergen. It relaxes the muscles in the airways, increases heart rate, and raises blood pressure. It is crucial to administer epinephrine as soon as symptoms appear, as any delay can increase the chance of hospitalization and even lead to fatalities.

While anaphylaxis can affect anyone with severe allergies, certain factors increase the risk. These include a history of allergies, asthma, heart disease, or an irregular accumulation of a specific type of white blood cell called mastocytosis. It is important for individuals with known allergies to be aware of their triggers and carry the necessary emergency medications, such as an epinephrine auto-injector, at all times.

Allergic reactions and stroke symptoms

An allergic reaction occurs when the body's immune system overreacts to a foreign substance, known as an allergen. These allergens can be inhaled, ingested, or come into contact with the skin, eyes, nose, or mouth. Common allergens include pollen, peanuts, eggs, certain medications, and insect stings. During an allergic reaction, the immune system releases antibodies that bind to mast cells, causing them to release histamine and other chemicals, which lead to allergy symptoms. These symptoms can range from mild, such as itchy eyes and sneezing, to severe and life-threatening, known as anaphylaxis. Anaphylaxis can cause a drop in blood pressure, swelling, difficulty breathing, dizziness, nausea, and in some cases, lead to a fatal outcome.

On the other hand, a stroke is a serious medical condition that occurs when the blood supply to the brain is interrupted, resulting in brain damage. Stroke symptoms can arise suddenly and vary depending on the type of stroke and the area of the brain affected. Common stroke symptoms include sudden weakness, numbness, or paralysis on one side of the body, difficulty speaking or understanding speech, visual impairments, balance issues, severe headaches, and decreased responsiveness.

While allergic reactions and stroke symptoms share some similarities, it is crucial to distinguish between the two as their treatments differ. For allergic reactions, treatments aim to reduce the body's immune response and alleviate symptoms. This can include the use of antihistamines, decongestants, nasal steroids, asthma medications, and in severe cases of anaphylaxis, adrenaline injections. In contrast, stroke treatment focuses on restoring blood flow to the brain and minimizing brain damage. This may involve the use of medications, surgery, or other emergency medical procedures.

In rare cases, anaphylaxis has been associated with ischemic strokes. Ischemic strokes occur when there is a blockage in a blood vessel supplying blood to the brain, and they are typically caused by blood clots or plaque buildup. In one reported case, a patient with pre-existing vertebral artery hypoplasia (VAH) experienced an allergic reaction, leading to hypotension (low blood pressure) and subsequently suffered an ischemic stroke. This case highlights the potential link between severe allergic reactions and stroke-like symptoms, particularly in individuals with underlying vascular conditions.

However, it is important to note that allergic reactions and stroke symptoms are distinct medical conditions that require different treatments. If you suspect someone is experiencing either an allergic reaction or a stroke, immediate medical attention is crucial.

Allergens and the immune system

Allergies are an immune system response to an otherwise innocuous substance, known as an allergen. These allergens are usually proteins (or antigens) found in non-infectious substances, such as pollen, dust mites, latex, or certain foods. When an allergen enters the body, it is captured by antigen-presenting cells, which present them to the immune cells, particularly T cells. This initiates a cascade of immune responses, resulting in the production of allergen-specific IgE antibodies by B cells. These antibodies target only one type of allergen, which is why people can be allergic to one substance but not another.

Upon re-exposure to the allergen, the binding of the allergen to IgE-mast cells can trigger an aggressive and immediate immune response. Mast cells are granular cells that, when activated, release their contents into the bloodstream, including histamine, which causes blood vessels to expand. This results in local inflammation and the symptoms associated with allergies, such as clogged sinuses, skin inflammation, difficulty breathing, or stomach problems. In extreme cases, anaphylaxis can occur, which is a serious, systemic, and life-threatening allergic reaction. Anaphylaxis is characterised by respiratory and circulatory dysfunction and is usually associated with cutaneous and mucosal changes. It can be caused by foods, insect stings, and medications, and can be fatal if the circulatory and respiratory systems are severely compromised.

The prevalence of allergies is increasing, particularly in developed countries, and this trend is thought to be linked to changes in human lifestyle that have altered our exposure to microbes. The 'Hygiene Hypothesis' suggests that increased exposure to microorganisms correlates with a decreased tendency to develop allergies. This has evolved into the 'Old Friends Mechanism', which links the development of allergies to an individual's microbiome. According to this theory, exposure to a diverse range of microbes in early life helps develop a properly regulated immune system that does not overreact to harmless allergens. Changes in human lifestyle, such as less breastfeeding, smaller family size, and increased antibiotic use, have reduced our exposure to diverse microbes, potentially contributing to the rise in allergies.

Allergy immunotherapy or desensitisation can be used to eliminate a person's allergy by reversing their immune response to the triggering allergen. This involves administering the allergen in gradually increasing doses, eventually developing immunity or tolerance. While this treatment has been effective for allergies such as hay fever, house dust mite, and insect venom, more strategies are needed to treat other allergies.

Diagnosing allergies

Allergies are common, with around 30% of US adults and 40% of children experiencing them. An allergy is when your body reacts to something that is typically harmless, like pollen, dust, or animal fur. Allergens are the things that cause these allergic reactions, and they can be found in food, the environment, or certain materials.

• Medical History: When you visit an allergist, they will first take your medical history. They will ask about your health, any symptoms you are experiencing, and your family history of allergies or asthma. They will also inquire about your work, home, and eating habits to identify possible triggers for your allergy symptoms.
• Allergy Testing: Allergists use their expertise to select the most appropriate tests for diagnosing allergies. Skin testing is the preferred method and is usually the most accurate. However, blood tests may be ordered in specific situations.
• Skin Prick or Patch Test: This is the most common type of skin test. A small amount of the potential allergen is pricked or scratched into your skin to see if it reacts. This test is often used for common inhalant allergens like pollen and dust mites.
• Intradermal Test: This test is typically used to determine allergies to insect stings or penicillin. A small amount of the allergen is injected under the skin through a thin needle.
• Blood Tests: Blood testing can also be used to detect a patient's sensitivity to various allergens. It is useful for detecting allergies to medicines, foods, latex, venom, or other substances. However, blood tests are generally more expensive and take longer to provide results.
• Special Diet: Your doctor may also recommend a special diet where you avoid or reduce consuming a particular food item to observe if your symptoms improve.

It is important to note that the choice of test depends on various factors, including symptoms, environmental and occupational exposures, age, and even hobbies. The results of these tests are then interpreted along with your medical history to make a final diagnosis.

Treating allergies and allergic reactions

Allergies are very common, with over 50 million people in the United States experiencing an allergic reaction each year. They are caused by an overreaction of the body's immune system to typically harmless foreign substances, which are known as allergens. Allergens can be anything from food and medication to insects and the environment.

Allergic reactions can range from mild to life-threatening. Symptoms include sneezing, itchy and watery eyes, a runny nose, skin irritation, nausea and vomiting, swelling, and anaphylaxis. Anaphylaxis is a serious, systemic, and life-threatening allergic reaction that can lead to circulatory and respiratory failure and, ultimately, death.

The best way to treat and prevent allergic reactions is to identify the allergens that trigger them and avoid them, especially food allergens. When this is not possible or realistic, antihistamines or decongestants can be used to treat the symptoms when in contact with allergens.

Medication

• Antihistamines can help to treat most minor allergic reactions, regardless of the cause. They reduce the body's production of histamine, thereby reducing symptoms such as sneezing, watering eyes, and skin reactions. Examples include Claritin (loratadine) and Zyrtec (cetirizine).
• Nasal decongestant pills, liquids, and sprays can help reduce stuffiness, swollen sinuses, and related symptoms such as a sore throat or coughing. However, decongestants are not a long-term solution and should not be used for more than one week.
• Nonsteroidal anti-inflammatory drugs (NSAIDs) may help to temporarily reduce pain, swelling, and cramping caused by allergies.
• Asthma medications such as bronchodilators and inhaled corticosteroids can be used to treat allergic asthma.
• Oral cromolyn is a prescription medication that can help with food allergy symptoms.
• Drug desensitization therapy involves taking small doses of a medication that triggers an allergic reaction until the body can handle the dosage.
• Injections of the hormone epinephrine or adrenaline can be used to treat anaphylaxis. These are available as auto-injectors (EpiPens) that can be carried with you at all times.

Other Treatments

• A saline sinus rinse can be used to remove allergens and clear the airways when allergies cause sinus problems.
• For skin allergies, topical corticosteroid creams or tablets can be used.
• For environmental allergies, throat lozenges with soothing ingredients such as menthol, honey, or ginger can help. It is also recommended to shower and wash clothing after being exposed to an allergen.
• Immunotherapy, or allergy shots, can be used to treat chronic or severe allergies. This involves exposing the patient to small amounts of allergens and gradually increasing the dosage over several months to create a tolerance to the allergen.
• Sublingual immunotherapy involves tablets that dissolve under the tongue.
• Natural remedies such as dietary changes, supplements, and acupuncture may also help relieve symptoms.

Frequently asked questions