• Impaired immune systems. Those with autoimmune diseases, such as lupus (a chronic skin disease) or AIDS, should not undergo immunotherapy. Allergy shots in these patients can spur the creation of immunoglobulin g (IgG) antibodies, leading to the creation of antigen-antibody complexes. This process can bring about immune-related conditions.
  
  
• Heart disease (including high blood pressure). Patients with some heart conditions are not candidates for allergy-shot treatments. Those undergoing immunotherapy face a small risk of experiencing the life-threatening allergic reaction known as anaphylaxis, which is more likely to be fatal for those with heart conditions. 
  
  
• Beta-blocker use. Those who take beta blockers to treat high blood pressure or a heart condition may not be good candidates for immunotherapy. Beta blockers can counteract the effects of epinephrine, the only drug that effectively reverses the symptoms of anaphylaxis, a rare but life-threatening allergic reaction that can be triggered by testing.
  
  
• Monoamine oxidase inhibitor use. These antidepressants also counteract the effects of epinephrine, which is used to reverse the symptoms of anaphylaxis.
  
  
• Pregnancy. Pregnant women and those considering becoming pregnant should tell their physician before beginning a course of immunotherapy. Pregnancy does not preclude immunotherapy treatments, though it may be necessary for women to take steady allergy shot doses during the pregnancy (without increasing the dosage).
  
  
• Uncontrolled asthma. Many individuals with asthma can benefit from allergy shots, but asthmatics have a higher risk of experiencing anaphylaxis while undergoing immunotherapy. Those with asthma should not engage in immunotherapy unless their condition is under control.

Age may also play a role in the effectiveness of allergy shots. Immunotherapy is less likely to be effective in patients over 55. However, it still reduces the symptoms of many older patients. In very young children (under 5), allergy shots may not be advised. However, research has emerged that giving allergy shots to children under 5 may help slow or stop the development of allergies later in life. Research is continuing, and parents should discuss any questions regarding allergy shots with their physician.

Immunotherapy involves regular injections over a long period of time. Parents and healthcare providers must be sensitive to the fears that even older children have about needles. When allergy shots are recommended, fully explaining the immunotherapy process and talking with a child about his or her concerns can help alleviate their fears.