A cortisone shot is an injection of corticosteroid medication designed to reduce inflammation in a targeted area, such as a joint or tendon. These injections are often effective for treating pain associated with conditions like arthritis or tendinitis. Allergic reactions to the steroid or other components are exceedingly rare, but recognizing the symptoms is important. Reactions can range from mild, localized responses to severe, life-threatening systemic responses.
Differentiating Normal Injection Side Effects from Allergies
Many people experience temporary discomfort following a cortisone injection that is often mistaken for an allergy. This common, non-allergic reaction is frequently called a “cortisone flare” or “post-injection flare.” A cortisone flare occurs when the crystalline particles of the corticosteroid temporarily irritate the tissues around the injection site. This flare involves a short-lived increase in pain, swelling, and warmth, usually beginning within a few hours. Symptoms are generally self-limiting, peaking within 24 hours and resolving within 48 to 72 hours.
Other expected, non-allergic side effects include temporary facial flushing, a slight rise in blood sugar, or mild soreness from the needle. These common reactions do not involve an immune system overreaction and are not true allergic responses.
Localized Allergic Reactions at the Injection Site
A genuine localized allergic reaction indicates the immune system is responding inappropriately to the medication or its preservatives. These reactions are often delayed, appearing hours, days, or even weeks after the injection, and are characterized as delayed-type hypersensitivity. Unlike the short-lived cortisone flare, these symptoms persist or worsen over time.
Signs of a localized allergic reaction include severe, persistent itching, a distinct rash, or significant redness that spreads beyond the puncture mark. Some individuals may experience induration, which is a hardening and firm swelling of the tissue. The skin may also show signs of atrophy, such as dimpling or a lightening of the skin color (hypopigmentation) at the injection site.
Systemic and Severe Allergic Symptoms
The most dangerous allergic reactions are systemic, affecting multiple body systems, and are known as anaphylaxis. These are immediate hypersensitivity reactions, often occurring rapidly within minutes to an hour of the injection. Anaphylaxis is a medical emergency that requires immediate intervention.
Symptoms often begin with widespread skin involvement, such as hives or intense, generalized itching far from the injection site. Swelling of the soft tissues, known as angioedema, is a major warning sign and can affect the lips, tongue, or throat, leading to tightness. Respiratory symptoms are concerning and include difficulty breathing, wheezing, or shortness of breath.
The reaction can also affect the cardiovascular system, causing a rapid or irregular pulse, sudden dizziness, or feeling faint due to a drop in blood pressure. Gastrointestinal symptoms, such as vomiting or abdominal pain, may also accompany a severe systemic response. Any combination of these symptoms developing shortly after the shot warrants immediate attention.
When to Seek Emergency Medical Attention
Knowing when to act is important when a reaction is suspected. If you experience any signs of a systemic or severe allergic reaction, call for emergency medical assistance immediately. This includes difficulty breathing, swelling of the throat, tongue, or lips, or feeling faint or dizzy. Anaphylaxis can progress quickly, and immediate treatment with epinephrine is necessary to stabilize the patient.
For localized symptoms, such as persistent or worsening pain, spreading rash, or significant redness that lasts beyond three days, contact the prescribing physician. These localized reactions generally do not require emergency transport but do need medical evaluation. Reporting persistent or unusual symptoms allows the healthcare provider to determine if the reaction is a manageable side effect, a treatable localized allergy, or a sign of a more serious issue.