💊 Men's Health

Drug Allergies & Adverse Drug Reactions (Nigeria)

Q: If I reacted to penicillin once, can I ever take it again?

Possibly yes. 80–90% of people labelled as penicillin allergic actually tolerate penicillin when properly tested. Reactions from many years ago often represent non-allergic reactions (viral rash during illness when penicillin was given) or sensitivity that has waned. Formal allergy testing can clarify whether you are truly allergic.

Q: Can sulfa drugs (cotrimoxazole) be given to someone with HIV?

Cotrimoxazole is essential for PCP and toxoplasmosis prophylaxis in HIV. Cotrimoxazole hypersensitivity is common in HIV patients (due to immune activation). In mild cases, desensitisation protocols (gradually increasing doses) can be used to achieve tolerance. Severe reactions (SJS) are a contraindication — discuss with your HIV clinic.

Q: What is Stevens-Johnson syndrome and why is it dangerous?

SJS is a severe blistering reaction of the skin and mucous membranes, most commonly triggered by sulfonamides, anticonvulsants (carbamazepine, phenytoin), NSAIDs, and allopurinol. It is a medical emergency with up to 30% mortality (TEN — the severe form). Any blistering of the mouth, eyes, or genitals after starting a new drug is an emergency.

Q: The pharmacy gave me a different brand of paracetamol and I got a rash — am I allergic to paracetamol?

True paracetamol allergy is rare. The rash was more likely caused by a non-active ingredient (excipient) in one brand but not another, or coincided with a viral illness. True allergy to paracetamol should be confirmed by a specialist before concluding you cannot take it — it is one of the safest analgesics available.

Penicillin allergy, sulfa reactions, and managing adverse drug reactions safely in Nigeria

Adverse drug reactions (ADRs) and drug allergies are common in Nigeria, where self-medication and inadequate documentation of reactions contribute to preventable harm. Penicillin allergy is reported by many Nigerians, but 80–90% of those labelled as 'penicillin allergic' can actually tolerate it — the label was incorrectly applied or the sensitivity has waned. Removing an incorrect penicillin allergy label enables access to the most effective antibiotics. Severe drug reactions — Stevens-Johnson syndrome, anaphylaxis — are medical emergencies.

Signs and Symptoms

✓ Urticaria (hives) and angioedema — within 1 hour of drug ingestion (IgE-mediated, most serious)

✓ Maculopapular (morbilliform) rash — widespread flat-red rash, usually 7–14 days after starting drug

✓ Drug reaction with eosinophilia and systemic symptoms (DRESS) — fever, rash, lymphadenopathy, organ involvement

✓ Stevens-Johnson syndrome (SJS) / Toxic epidermal necrolysis (TEN) — blistering of skin and mucous membranes — EMERGENCY

✓ Fixed drug eruption — same site of rash each time the drug is taken

✓ Drug fever — temperature rise without other cause

✓ Anaphylaxis — collapse, throat closure, wheeze (with any drug but especially IV medications, vaccines, contrast dye)

Risk Factors

HIV infection — dramatically higher rates of drug hypersensitivity (especially to cotrimoxazole, nevirapine, abacavir)
HLA-B*57:01 — genetic marker for abacavir hypersensitivity — tested before starting in HIV treatment
Previous drug allergy — cross-reactivity between related drugs
Viral infections — increase rates of drug-induced rash (e.g., ampicillin rash in glandular fever is not true allergy)
Repeated exposures to the same drug — sensitisation
Female sex — higher rates of most drug hypersensitivity reactions

When to Seek Help

EmergencyBlistering of skin or mucous membranes (mouth, genitals, eyes) after starting a new drug — Stevens-Johnson syndrome. Stop the drug and go to A&E immediately

EmergencyThroat tightening, difficulty breathing, collapse after a drug — anaphylaxis. Adrenaline and call 112

UrgentHigh fever + widespread rash + swollen lymph nodes after starting a new medication — possible DRESS syndrome

Same dayAny new rash after starting a medication — photograph it and call your prescriber

RoutineReview of 'penicillin allergy' label — allergy testing in most cases confirms the label is incorrect

Tests & Diagnosis

🧪 Skin prick test and intradermal testing for penicillin

Can confirm or exclude true IgE-mediated penicillin allergy. Available at allergy clinics. Followed by supervised oral amoxicillin challenge if tests negative — removes the label in most cases

🧪 Patch testing

For delayed contact drug reactions and fixed drug eruption — identifies the causative agent

🧪 Full blood count with differential

Eosinophilia in DRESS syndrome; thrombocytopenia in heparin-induced thrombocytopenia

🧪 Liver and renal function

Organ involvement in DRESS or severe reactions

🧪 HLA typing

HLA-B*57:01 before abacavir (HIV treatment) — prevents potentially fatal hypersensitivity. HLA-B*15:02 before carbamazepine in Southeast Asian patients — SJS risk

🧪 Drug levels (e.g., vancomycin)

Distinguishes toxicity from allergy in some cases

Treatment Options

STOP the causative drug immediately

In any suspected drug reaction, stop the most likely causative drug first. If multiple drugs, stop all non-essential medications

Stevens-Johnson syndrome / TEN management

Admit to burns unit or ICU. Stop causative drug. Wound care (like severe burns). Eye and genital mucosal care. IV fluids and nutritional support. Ophthalmology review urgently — eye involvement causes blindness if untreated. Ciclosporin or IVIG in selected cases — discuss with specialist

DRESS syndrome management

Stop causative drug. Systemic corticosteroids for severe organ involvement. Monitor LFTs, FBC for weeks after. Carries significant mortality — up to 10%

Anaphylaxis to a drug

Adrenaline (epinephrine) 0.5 mg IM (anterolateral thigh). IV chlorphenamine 10 mg and IV hydrocortisone 200 mg as adjuncts. IV fluids for hypotension. Observe for minimum 6–12 hours for biphasic reaction

Penicillin allergy delabelling

For patients labelled 'penicillin allergic' who need assessment — structured history + skin testing + oral challenge under supervision. Removes the label in 80–95% of cases. Enables access to safer, cheaper, more effective antibiotics

Alternative antibiotics if true penicillin allergy confirmed

Cephalosporins have <1% cross-reactivity with penicillin in truly allergic patients (most can be given). Azithromycin, clindamycin, or vancomycin for specific situations. Avoid empirical broadening of antibiotic choice based on unconfirmed allergy

Documentation and medical alert

Document all drug reactions clearly: drug name, reaction type, date, treatment. Alert bracelet for severe allergy. Inform all future healthcare providers

Frequently Asked Questions

If I reacted to penicillin once, can I ever take it again?

Possibly yes. 80–90% of people labelled as penicillin allergic actually tolerate penicillin when properly tested. Reactions from many years ago often represent non-allergic reactions (viral rash during illness when penicillin was given) or sensitivity that has waned. Formal allergy testing can clarify whether you are truly allergic.

Can sulfa drugs (cotrimoxazole) be given to someone with HIV?