What are common immediate allergic or systemic reactions to corticosteroid epidural injections?

1. Why patients feel flushed, light‑headed or nauseated right after an ESI — common systemic effects revealed

Prospective series and clinical reviews consistently report that the most frequent immediate, non‑allergic systemic effects after epidural steroid injections are facial flushing, transient hyperglycemia, nausea, headache, dizziness, and vasovagal fainting. A large prospective cohort found about 30% of injections were followed by systemic reactions, with facial flushing occurring in roughly 23% of those reactions ^[1]. Clinical practice guides and patient information from specialty centers list short‑term cardiovascular changes (transient hypertension or palpitations), insomnia, mood alterations, gastrointestinal upset, and transient rises in blood glucose—effects that typically resolve within hours to days but may be clinically significant in diabetics or those with cardiac disease ^{[2] [4] [5]}. These immediate systemic responses are often transient and dose‑ and patient‑dependent.

2. When the reaction is allergic: hives, angioedema and rare anaphylaxis — what the evidence shows

Allergic hypersensitivity events—immediate urticaria, angioedema, or anaphylactic shock—are established but less common after epidural corticosteroid procedures. Studies that separate out reactions to radiographic contrast media report higher proportions of urticaria and multisystem anaphylaxis tied to the contrast rather than necessarily to the steroid: one series of contrast‑hypersensitive patients undergoing epidurals found urticaria in 52% and multisystem anaphylaxis in 28% of reactions, illustrating how inclusion of contrast reactions inflates allergic event counts ^[3]. Reviews of corticosteroid injections list hypersensitivity as a possible immediate event alongside other systemic effects, but they also caution that true steroid allergy is relatively rare compared with systemic pharmacologic effects ^{[6] [2]}. Distinguishing steroid allergy from dye or anesthetic allergy is critical for risk attribution.

3. Systemic pharmacologic effects that appear quickly but aren’t allergic — cortisol suppression, glucose and mood shifts

Several sources document immediate and short‑term systemic pharmacologic effects from epidural corticosteroids that are not allergic immune reactions. Randomized and observational data show adrenal suppression and measurable cortisol decreases after epidural steroid doses; one report found about 20% of patients had >50% reduction in morning cortisol at three weeks, signifying systemic HPA axis impact despite the local route ^[7]. Reviews and adverse‑effect summaries also list acute hyperglycemia, transient hypertension, fluid retention, mood swings, insomnia, and neuropsychiatric symptoms—all pharmacologic sequelae of systemic corticosteroid exposure rather than immunologic allergy ^{[2] [6]}. These effects are important for clinical monitoring, especially in diabetic, hypertensive or psychiatric patients.

4. How common are these problems in routine practice — reconciling different numerators and denominators

Reported frequencies diverge because studies differ in definitions, follow‑up timing, and whether they count reactions to contrast, local anesthetic, or steroid. A large prospective cohort reported systemic reactions after roughly 30% of injections, with many events being minor and transient ^[1]. Other clinic summaries emphasize that true allergic reactions are rare, while non‑allergic immediate effects (flushing, nausea, blood sugar rise) are relatively common and often under‑reported ^{[4] [5]}. Contrast‑focused studies elevate allergic‑reaction percentages by studying patients already hypersensitive to iodinated dye ^[3]. Interpretation requires noting whether the denominator is per‑patient, per‑injection, and whether contrast or adjuncts are included.

5. Clinical implications: screening, monitoring and attribution to guide decisions

Practical guidance emerging from reviews and clinical resources is to screen for diabetes, hypertension, psychiatric illness, and prior contrast or drug allergies before epidural steroid injections, to observe patients briefly after the procedure for vasovagal or allergic reactions, and to distinguish pharmacologic steroid effects from immunologic allergy when events occur ^{[5] [2] [8]}. In cases of suspected allergic reaction, evaluate the timing, associated exposures (contrast, anesthetic), and symptom pattern (urticaria/airway compromise vs flushing/nausea) to assign causality and plan future care. Accurate attribution directs whether steroids can be reused or should be avoided in favor of alternative strategies.