Patient Information and Handouts

If you have certain types of allergies, allergy shots may help with your symptoms. You may be a candidate for allergy shots if you have: 

  • Hay fever 

  • Allergic asthma 

  • Life-threatening allergies to insect stings 

  • Allergies to pollen, pet dander or dust mites 

Another name for allergy shots is “allergen immunotherapy injections.” They are the only medical treatment known to help with these types of allergies.  

Allergy shots are not meant to “cure” your allergies. However, they can make you less sensitive to your allergens. This means you may have fewer symptoms. 

How do allergy shots work? 

Allergy shots work by exposing you to the thing that is triggering your allergies. The exposure can make you less sensitive to that allergen. The shots work best for people with moderate to severe symptoms.  

Before your doctor prescribes allergy shots, they may want you to try making changes to your environment first to see if that will help. In some cases, you may need to make changes to your prescription medications, as well.  

Most people who get allergy shots start with a course that lasts for 6-12 months. During this time, your sensitivity to your allergens may decrease. If they do, your symptoms should improve.  

It is important to get your allergy shots at the right time. Your doctor will let you know when and how often you need them. If you do not get your shots in time, your doctor may need to adjust the dose. You should let your doctor know right away if this happens. 

Getting allergy shots involves two phases. The phases are: 

  1. The build-up phase. 

  1. The maintenance phase. 

  • In the build-up-phase, you will get allergy shots 1-2 times a week (some people may need more). Every time you get a shot, the amount of allergen you receive will increase. The build-up phase can last 2-6 months. Some patients may need a “rush” protocol for their allergy shots. Your doctor will let you know if this is an option for you. 

  • The maintenance phase starts once the shots in the build-up phase start working. The dosage varies by person, depending on how sensitive they are to various allergens. Once you are in this phase, you will still need to get shots. You just won’t need to get the as often as before. Most likely, you will get maintenance shots every 2-4 weeks. 

Reactions to Allergy Shots 

It is possible to have an allergic reaction to the allergy shot itself, especially if you exercise right after getting a shot. Heavy exposure to pollen at the same time can also trigger a reaction to an allergy shot.  

Reactions can be local or systemic.  

  • A local reaction is swelling at the injection site.  

  • A systemic reaction is one that affects your whole body. Symptoms include sneezing, itchy eyes/nose/throat, nasal congestion, hives, flushing, lightheadedness, trouble breathing, nausea, vomiting or wheezing. Rarely, systemic reactions can be serious or even life-threatening. This is more likely to happen if you have asthma. People with asthma should tell their doctor before getting an allergy shot, especially if you have: 

  • Worsening asthma symptoms. 

  • Asthma that isn’t improving with the use of medication.  

Rarely, people can have life-threatening systemic reactions, such as anaphylaxis, to allergy shots. This is more likely to happen when someone exercises. In general, any type of reaction is more likely if you have a lot of exposure to pollen during pollen season or if you exercise after getting an allergy shot.  

If you have any symptoms of a systemic reaction after your allergy shot, it is important that you let us know before you get your next one. You should also let us know about any updates to your medical history and/or the medication you are taking.  

Because reactions can happen, you will need to wait 30 minutes after your shot before leaving our office. For patients who are 14 years of age or younger, a parent or legal guardian must wait with them. You should only get allergy shots at a clinic that has qualified medical staff on site that can treat any reactions that may occur. 

Unless your doctor tells you otherwise, you should not get allergy shots if you take beta-blocker medication. This is because beta blockers can prevent the treatments for reactions to allergy shots from working. 

Penicillin allergy is the most commonly reported drug allergy in the United States. Some reactions (hives, flushing, itchiness) affect the skin. More serious life-threatening anaphylaxis (wheezing, low blood pressure, vomiting, rash) also happen. 

Although often reported as an allergy, studies show that:  

  • Over 90% of people who report a penicillin allergy are actually not allergic (negative) when tested. 

  • More than half of patients lose their sensitivity to penicillin after 5 years, and 8 out of 10 patients lose it after 10 years. 

If you have a penicillin allergy, you are more likely be given less effective and more harmful antibiotics. You may also have higher rates of treatment failure, infections from the hospital and medical costs. This is why you should have an allergist do a full evaluation of this allergy. 

What are the steps to test for a penicillin allergy? 

You will come to our clinic for your evaluation. Based on your history, your doctor will decide if you need skin testing or if you can go straight to an observed challenge. 

Skin testing 

  1. We place a small amount of penicillin on the skin. 

  1. We use a small device to prick the skin. 

  1. If there is no reaction (rash, redness, itchiness), we inject small amounts of penicillin under the skin. 

Observed ingestion/challenge 

  1. You take a small amount of amoxicillin or other penicillin by mouth. 

  1. We monitor you for a short amount of time. 

  1. If you do not have a reaction, we then give you the full dose. 

  1. We continue to observe you for a longer period to make sure you do not have a reaction. If there is any sign of a reaction, we may give you medicine to treat your symptoms. 

What are the risks and benefits? 

For skin testing alone, the risk is very low. Some patients may get irritation at the site of the testing, but systemic reactions are exceedingly rare. This is all done at the OHSU Allergy and Immunology Clinic, so you can be closely monitored throughout the process.  

The observed challenge carries a risk of having an allergic reaction. Your Allergy provider considers your history and risk factors before deciding to proceed with the challenge. You will be closely monitored in the Allergy Clinic by both physicians and nurses throughout the process and can quickly address any side effects that may occur (this is rare).  

Benefits: Patients that carry a penicillin allergy label often receive alternative antibiotics for infections that would have been treated with a penicillin antibiotic. These alternative antibiotics are often not as effective (higher rate of treatment failure) and typically carry more side effects. Studies have shown that having a penicillin allergy label is associated with longer hospital stays, higher rate of readmission, higher treatment failure rates, more surgical-site infections, and more side effects from medications (such as C. difficile and MRSA infections). Removing the allergy can be done safely and leads to improved medical care in the future. 

Pregnancy: Ampicillin and other penicillin antibiotics are often first-line for infections that may occur during pregnancy due to their proven safety record. Women that have a penicillin allergy label during pregnancy have been associated with longer hospital stays and increased risk of C-sections. We work closely with our obstetricians and midwives to remove penicillin allergy labels when safe to do so in women currently pregnant or plan to become pregnant.   

What happens after penicillin testing? 

If the testing reveals you are not allergic to penicillin, we will: 

  • Remove penicillin from your allergy list at OHSU. 

  • Give you a letter and wallet card to provide proof you are no longer allergic to penicillin. 

Please let your pharmacy and other providers know about the change to your allergy list. 

You may develop a very late reaction to penicillin days or weeks after testing. If this happens, please call us to discuss your symptoms.  


Drug allergies are a common complaint with over 35% of patients reporting at least 1 drug on their allergy list. The types of reported reactions range from skin findings only (hives, flushing, itchiness) to life-threatening anaphylaxis (wheezing, low blood pressure, vomiting, rash). Studies have shown that patients with a reported drug allergy often are prescribed less effective and more toxic medications as alternatives. Therefore, having a thorough evaluation of this allergy by an allergist can drastically affect patient outcomes. 

What to Expect? 

You will come to the OHSU Clinic for evaluation of this allergy. Based on your history, your physician will decide if skin testing is needed or if you can go straight to an observed challenge (taking the medication here in the office with close observation by the medical staff).  

Skin testing (if needed) – Skin testing requires placing the medication of concern on the skin. Skin pricking will be performed with a small prick device. If negative, small amounts of the medication may be injected under the skin for intradermal testing. 

Oral ingestion/challenge – A set amount of the medication in question will be given to you either by mouth or injection. After a short observation period without reaction, a larger dose may then be given. We will observe you in clinic for an extended period of time to ensure you do not have a reaction to the medication. If there is any sign of a reaction, you will be treated for the reaction to prevent worsening of your symptoms.  

What to do after the test? 

If you are found not to be allergic to the medication in question after testing is complete, we will remove it from your allergy list at OHSU. We will provide you with documentation to provide proof that you are no longer allergic to the medication. Please inform your other providers and pharmacy of this change in your allergy list. 

You may develop a very late reaction to the medication days to weeks after the test. Please call the OHSU Allergy Clinic to discuss your symptoms.