PCOS Treatment When to Call Your Healthcare Provider About an Injection Side Effect Knowing the signs can prevent an emergency situation By Nicole Galan, RN Nicole Galan, RN Facebook LinkedIn Twitter Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book." Learn about our editorial process Updated on July 20, 2020 Medically reviewed Verywell Health articles are reviewed by board-certified physicians and healthcare professionals. These medical reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Anita Sadaty, MD Medically reviewed by Anita Sadaty, MD Facebook LinkedIn Twitter Anita Sadaty, MD, is board-certified in obstetrics-gynecology. She is a clinical assistant professor at Hofstra Northwell School of Medicine and founder of Redefining Health Medical. Learn about our Medical Expert Board Print Injections are a way of delivering treatment for many different health conditions and preventative care, including vaccines. Most often, injections are perfectly safe and cause only minor discomfort. However, as with all medications, there may be some adverse reactions or side effects. Ariel Skelley / Getty Images These kinds of reactions are often due to an infection or allergy. Some may be minor and easily treated, while others may be far more serious and lead to a potentially deadly, all-body reaction (such as anaphylaxis or sepsis). Symptoms can vary depending on if the shot was subcutaneous (under the skin), intravenous (in a vein), or intramuscular (in a muscle). This article explains reactions that you should be aware of and what to do if you experience them. High Fever Tom Merton/Getty Images Fevers higher than 101 F following an injection warrant a call to your healthcare provider or visit the nearest emergency room. That's because the fever may indicate an infection caused by needle contamination or an allergic reaction to the medication itself. Both are serious. By and large, allergies tend to happen quickly, while symptoms of an infection may take one to 10 days to appear. While many infections occur due to a self-administered injection, such as with diabetes or autoimmune disorders. However, they can also happen at the healthcare provider's office or hospital if the person administering the injection does not adhere to aseptic techniques. Extreme Pain at the Injection Site Fertnig/Getty Images While most people dislike the idea of a shot, the good news is it is usually over quickly and causes little pain. However, if the pain persists or worsens, you should call a healthcare provider and have it checked out. While it is not uncommon to have localized swelling or redness for a day or two following an injection (or even longer for certain types of intramuscular shots), some symptoms warrant further investigation. These include: Injection site that is tender to the touchFeverBody achesCreeping discoloration In some cases, the pain may be extreme but not particularly dangerous (such as when an intramuscular injection accidentally hits the sciatic nerve). But, at other times, it may be due to an infection that might only get worse if it's not untreated. Vaccine Side Effect vs. an Adverse Effect Swelling or Hardness Under the Skin PhotoAlto/Michele Constantini/Getty Images While swelling and minor bruising can happen after a shot, they usually get better within a day or so. However, if swelling and discoloration persist, it may signify an infection. Abnormal swelling that feels soft, mushy, and painful may indicate a developing abscess. An abscess is a walled-off collection of pus. It is often warm to the touch and accompanied by enlarged lymph nodes, small bean-shaped glands that are part of the immune system. You should never squeeze abscesses. That's because to prevent infection from spreading throughout the body, a healthcare provider must properly drain it. If you try yourself, it could burst under the skin and spread the infection through the bloodstream, causing a potentially life-threatening blood infection known as sepsis. Signs a bump may be an abscess include: The bump oozes: While a bit of drainage following an injection may be expected (caused by medication leaking out of the needle track), a doctor should look at any discolored or abnormal discharge immediately.The swelling grows: If the bump is small and you're not sure if it's an abscess, take a pen and draw a circle along the border. If it starts to expand beyond the edge or fails to go away in several hours, call a healthcare provider to look at it as soon as possible. A Sudden, All-Body Reaction Edward McCain/Getty Images Following an injection, the most severe reaction is an all-body allergic response known as anaphylaxis. This type of response can occur if the body reacts adversely to the injected medication, causing a cascade of severe and potentially life-threatening symptoms. Anaphylaxis develops very quickly and needs to be treated immediately with a shot of epinephrine (adrenaline). The first signs of anaphylaxis may be similar to those for an allergy, including a runny nose and congestion (rhinitis), and an itchy skin rash. However, within 30 minutes or so, more severe symptoms can develop, including: Coughing, wheezing, and shortness of breath Chest tightness Hives Dizziness or fainting Rapid or irregular heartbeat Weak pulse Facial swelling Swollen or itchy lips or tongue Difficulty swallowing A blue-ish tinge to the lips, fingers, or toes (cyanosis) Pale, clammy skin Nausea, vomiting, or diarrhea People who have anaphylaxis often report having a feeling of impending doom and panic. Anaphylaxis can lead to shock, coma, or even death if left untreated. Symptoms of Anaphylactic Shock Summary Injection site reactions are usually mild when they do occur. However, sometimes they can indicate something more serious, like an infection or allergic reaction. High fever, swelling, drainage from the injection site, severe pain, or a whole-body response are all reasons to see a healthcare provider for an evaluation. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit 2 Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Mishra P, Stringer MD. Sciatic nerve injury from intramuscular injection: a persistent and global problem. Int J Clin Pract. 2010;64(11):1573-1579. doi:10.1111/j.1742-1241.2009.02177.x Simons FE. Anaphylaxis pathogenesis and treatment. Allergy. 2011;66 Suppl 95:31-4. doi:10.1111/j.1398-9995.2011.02629.x Additional Reading Pugliese, G.; Gosnell, C.; Bartley, G. et al. "Injection practices among clinicians in the United States health care settings." Amer J Infect Cont. 2010; 38(10):789-798.