Can Covid Vaccine Cause Serious Allergic Reactions

Vaccine and allergic reaction patterns

Allergic Reaction and Covid Vaccine

A vaccine reaction is an individual’s response to the inherent properties of the vaccine. Vaccine-related adverse reactions are generally mild, but on  many occasions, patients can experience severe or even life-threatening reactions. Reactions to vaccines may be delayed or prolonged, potentially lasting even several days. Generally, reactions typically occur within a day or two of immunization. Adverse events also emanate from human errors – mostly due to storage and temperature lapses. Presently, there is not much published literature about the effectiveness of the COVID-19 vaccines. Irrespective of an individual’s allergy history, people with allergies should not get the vaccine for now. Earlier, we have discussed the ethical issues of covid-19 vaccines. Here, we discussed probable allergic reactions to COVID-19 vaccines. 

Overview of Allergic Reactions                   

Local and systemic vaccine reactions such as pain or fever can occur as part of the immune response. But for some people, who are allergic to many substances, can trigger serious reactions. After the emergency approval of a COVID vaccine in the UK, some people had allergic reactions. If you have an allergy, your immune system overreacts to an allergen by producing antibodies called Immunoglobulin E (IgE). These antibodies travel to cells that release chemicals, causing an allergic reaction.

Normally, the immune system—which includes antibodies, white blood cells, mast cells, complement proteins, and other substances—defends the body against foreign substances (called antigens). However, in susceptible people, the immune system can overreact when exposed to certain substances (allergens) in the environment, foods, or drugs, which are harmless in most people. The result is an allergic reaction. Some people are allergic to only one substance. Others are allergic to many.

In many allergic reactions, the immune system, when first exposed to an allergen, produces a type of antibody called immunoglobulin E (IgE). IgE binds to a type of white blood cell called basophils in the bloodstream and to a similar type of cell called mast cells in the tissues. The first exposure may make people sensitive to the allergen (called sensitization) but does not cause symptoms.

When sensitized people subsequently encounter the allergen, the basophils and mast cells with IgE on their surface release substances (such as histamine, prostaglandins, and leukotrienes) that cause swelling or inflammation in the surrounding tissues. Such substances begin a cascade of reactions that continue to irritate and harm tissues. These reactions range from mild to severe.

Vaccine and Allergic Reaction Patterns

Some vaccine reactions follow some common patterns. However, there is considerable variability in the pattern of reactions based on person’s disease history, genetical construct and immunity. The severity grades of the allergic reactions are classified into four groups: mild intermittent, mild persistent, moderate persistent and severe persistent. Adverse reactions to vaccine typically occur within a day or two of immunization. 

Vaccine and allergic reaction patterns

Vaccine and allergic reaction patterns

Associated symptoms

It is possible that people who experience an anaphylactoid reaction to the COVID vaccine may suffer from various other symptoms. Some of them are as follows.

  1. High fever, runny noses and sneezing
  2. Dizziness 
  3. Difficulty in breathing, respiratory reactions 
  4. Confusion and anxiety
  5. A fast heartbeat
  6. Sudden moments of unconsciousness
  7. Sweaty skin

Anaphylaxis and Anaphylactoid Reactions

Anaphylaxis (an-a-fi-LAK-sis) is a serious, life-threatening allergic reaction. The most common anaphylactic reactions are to foods, insect stings, medications and latex. If you are allergic to a substance, your immune system overreacts to this allergen by releasing chemicals that cause allergy symptoms. Anaphylactic reactions typically begin within 15 minutes of exposure to the allergen. Anaphylaxis is an acute, potentially life-threatening hypersensitivity reaction. When you come into contact with the allergen, your immune system’s reaction can inflame your skin, sinuses, airways or digestive system. Hay fever, or allergic rhinitis, causes itchy, stuffy, and runny noses and sneezing. You can see the details of the human immunity system in the figure below. 

Human Immunity System and immunoglobulins 

Human Immunity System and immunoglobulins

Anaphylaxis is an allergic response by the body to external substances such as food, medicines and vaccines.  The manifestations of anaphylaxis include effects on the cardiovascular, respiratory, gastrointestinal systems and the skin by way of severe rash.  The blood pressure can drop, and breathing can become difficult.

Anaphylactoid reactions

Anaphylactoid reactions are allergic reactions that share some of the characteristics of anaphylaxis but are slightly less severe. Anaphylaxis involves a type of antibody called IgE which recognizes a specific allergen and triggers the release of chemicals from immune cells on exposure to that allergen.  Anaphylactoid reactions trigger the same responses as anaphylaxis but do not involve IgE antibodies.


Sources: CDC


It is possible that people with allergies may experience sever reactions to covid vaccine. In most cases, at least two organ systems react in the body: First, respiratory system and the skin. Sometimes the gastro-intestinal-system reacts, and in many cases the cardiovascular system reacts. Nonetheless, allergic people must go to the hospital emergency department, where they can be closely monitored and treatment can be adjusted as needed. Irrespective of an individual’s allergy history, people with allergies should not get the vaccine for now.