Immunizations are preventative treatments that keep people from contracting various diseases. These vaccines can inoculate patients against measles, mumps and rubella; diphtheria, tetanus and pertussis; influenza and many other health risks. However, these same vaccines can trigger symptoms in some patients who have allergies.

Not all reactions to vaccines are allergic in nature. Many patients will experience side effects to immunization procedures that are not IgE-mediated. These reactions can be localized (limited to part of the body) or generalized (systemic, and appearing throughout the body). Symptoms include:

• Localized
• Pain
• Warmth
• Tenderness
• Swelling
• Erythema (skin redness caused by dilatation and congestion of the capillaries)
  
  
• Generalized
• Fever

Such side effects usually are considered minor and do not prohibit further use of the vaccine. In addition, some physical causes related to the actual act of injecting can mimic an allergic reaction.

In some cases, vaccine-related reactions manifest as a skin irritation such as a rash (contact dermatitis) or hives. In other cases, symptoms can be more severe, such as the potentially life-threatening reaction called anaphylactic shock.

Signs and symptoms of a severe allergic reaction may include:

• Difficulty breathing (e.g., wheezing)
• Hoarseness
• Weakness
• Dizziness
• Swelling of the mouth and throat.
• Paleness
• Rapid heart beat

Allergic reactions to a vaccine typically occur within several minutes to several hours after the vaccine is given. Parents of children displaying the signs of symptoms of a severe allergic reaction should seek immediate emergency medical attention for the child. Parents with children showing other unusual symptoms (e.g., high fever, behavior changes) after receiving a vaccine should contact their physician.  

Children make up the majority of immunization patients. Parents may feel torn between a desire to protect their child from disease, and a fear that doing so could trigger potentially life-threatening allergies.

However, recent research indicates that allergic reactions to immunization therapy are rare.  Only about one in a million doses of a vaccine triggers a severe allergic reaction, according to the U.S. Centers for Disease Control and Prevention (CDC). Patients most likely to react are those with food or medication allergies, but even among those populations there is very little likelihood of suffering severe reactions.

Vaccines are safe. Each vaccine must undergo rigorous testing to ensure safety before the U.S. Food and Drug Administration (FDA) approves it for use. This process can take a decade or longer. In addition, the FDA and the CDC monitor all approved vaccines through a program known as the Vaccine Adverse Event Reporting System.

Failure to vaccinate a child against certain diseases dramatically raises the chances of health risks for the child. Children are more likely to contract common, contagious, preventable and potentially deadly diseases. This raises the potential for the re-emergence of diseases in areas where they were once almost eradicated.

Experts agree that for most patients, the benefits of vaccination far outweigh the small risks involved.