1 Recommendations

The following guidance is based on the best available evidence. The full guideline gives details of the methods and the evidence used to develop the guidance.

All recommendations apply to adults, children and young people.

People have the right to be involved in discussions and make informed decisions about their care, as described in your care.

Making decisions using NICE guidelines explains how we use words to show the strength (or certainty) of our recommendations, and has information about professional guidelines, standards and laws (including on consent and mental capacity), and safeguarding.

1.1 Assessment

1.1.1 When assessing a person presenting with possible drug allergy, take a history and undertake a clinical examination. Use the following boxes as a guide when deciding whether to suspect drug allergy.

Boxes 1–3 Signs and allergic patterns of suspected drug allergy with timing of onset[2]

Box 1 Immediate, rapidly evolving reactions

Anaphylaxis – a severe multi‑system reaction characterised by:

  • erythema, urticaria or angioedema and

  • hypotension and/or bronchospasm

Onset usually less than 1 hour after drug exposure (previous exposure not always confirmed)

Urticaria or angioedema without systemic features

Exacerbation of asthma (for example, with non‑steroidal anti‑inflammatory drugs [NSAIDs])

Box 2 Non‑immediate reactions without systemic involvement

Widespread red macules or papules (exanthema‑like)

Onset usually 6–10 days after first drug exposure or within 3 days of second exposure

Fixed drug eruption (localised inflamed skin)

Box 3 Non‑immediate reactions with systemic involvement

Drug reaction with eosinophilia and systemic symptoms (DRESS) or drug hypersensitivity syndrome (DHS) characterised by:

  • widespread red macules, papules or erythroderma

  • fever

  • lymphadenopathy

  • liver dysfunction

  • eosinophilia

Onset usually 2–6 weeks after first drug exposure or within 3 days of second exposure

Toxic epidermal necrolysis or Stevens–Johnson syndrome characterised by:

  • painful rash and fever (often early signs)

  • mucosal or cutaneous erosions

  • vesicles, blistering or epidermal detachment

  • red purpuric macules or erythema multiforme

Onset usually 7–14 days after first drug exposure or within 3 days of second exposure

Acute generalised exanthematous pustulosis (AGEP) characterised by:

  • widespread pustules

  • fever

  • neutrophilia

Onset usually 3–5 days after first drug exposure

Common disorders caused, rarely, by drug allergy:

  • eczema

  • hepatitis

  • nephritis

  • photosensitivity

  • vasculitis

Time of onset variable

1.1.2 Be aware that the reaction is more likely to be caused by drug allergy if it occurred during or after use of the drug and:

  • the drug is known to cause that type of reaction or

  • the person has previously had a similar reaction to that drug or drug class.

1.1.3 Be aware that the reaction is less likely to be caused by drug allergy if:

  • there is a possible non‑drug cause for the person's symptoms (for example, they have had similar symptoms when not taking the drug) or

  • the person has gastrointestinal symptoms only.

Measuring serum tryptase after suspected anaphylaxis

1.1.4 After a suspected drug‑related anaphylactic reaction, take 2 blood samples for mast cell tryptase in line with recommendations in the NICE guideline on anaphylaxis.

1.1.5 Record the exact timing of both blood samples taken for mast cell tryptase:

  • in the person's medical records and

  • on the pathology request form.

1.1.6 Ensure that tryptase sampling tubes are included in emergency anaphylaxis kits.

Measuring serum specific immunoglobulin E

1.1.7 Do not use blood testing for serum specific immunoglobulin E (IgE) to diagnose drug allergy in a non‑specialist setting.

1.2 Documenting and sharing information with other healthcare professionals

Recording drug allergy status

1.2.1 Document people's drug allergy status in their medical records using 1 of the following:

  • 'drug allergy'

  • 'none known'

  • 'unable to ascertain' (document it as soon as the information is available).

1.2.2 If drug allergy status has been documented, record all of the following at a minimum:

  • the drug name

  • the signs, symptoms and severity of the reaction (see recommendation 1.1.1)

  • the date when the reaction occurred.

Documenting new suspected drug allergic reactions

1.2.3 When a person presents with suspected drug allergy, document their reaction in a structured approach that includes:

  • the generic and proprietary name of the drug or drugs suspected to have caused the reaction, including the strength and formulation

  • a description of the reaction (see recommendation 1.1.1)

  • the indication for the drug being taken (if there is no clinical diagnosis, describe the illness)

  • the date and time of the reaction

  • the number of doses taken or number of days on the drug before onset of the reaction

  • the route of administration

  • which drugs or drug classes to avoid in future.

Maintaining and sharing drug allergy information

1.2.4 Prescriptions (paper or electronic) issued in any healthcare setting should be standardised and redesigned to record information on which drugs or drug classes to avoid to reduce the risk of drug allergy.

1.2.5 Ensure that drug allergy status is documented separately from adverse drug reactions and that it is clearly visible to all healthcare professionals who are prescribing drugs.

1.2.6 Check a person's drug allergy status and confirm it with them (or their family members or carers as appropriate) before prescribing, dispensing or administering any drug (see also recommendation 1.3.4). Update the person's medical records or inform their GP if there is a change in drug allergy status.

1.2.7 Ensure that information about drug allergy status is updated and included in all:

  • GP referral letters

  • hospital discharge letters.

1.2.8 Carry out medicines reconciliation for people admitted to hospital in line with recommendations in the NICE guideline on medicines optimisation: the safe and effective use of medicines to enable the best possible outcomes.

Documenting information after specialist drug allergy investigations

For recommendations on referral to specialist services see section 1.4.

1.2.9 After specialist drug allergy investigations, allergy specialists should document:

  • the diagnosis, drug name and whether the person had an allergic or non‑allergic reaction

  • the investigations used to confirm or exclude the diagnosis

  • drugs or drug classes to avoid in future.

1.3 Providing information and support to patients

1.3.1 Discuss the person's suspected drug allergy with them (and their family members or carers as appropriate) and provide structured written information (see recommendation 1.2.3). Record who provided the information and when.

1.3.2 Provide information in line with the recommendations in the NICE guideline on patient experience in adult NHS services.

1.3.3 Ensure that the person (and their family members or carers as appropriate) is aware of the drugs or drug classes that they need to avoid, and advise them to check with a pharmacist before taking any over‑the‑counter preparations.

1.3.4 Advise people (and their family members or carers as appropriate) to carry information they are given about their drug allergy at all times and to share this whenever they visit a healthcare professional or are prescribed, dispensed or are about to be administered a drug.

Providing information and support to people who have had specialist drug allergy investigations

For recommendations on referral to specialist services see section 1.4.

1.3.5 Allergy specialists should give the following written information to people who have undergone specialist drug allergy investigation:

  • the diagnosis – whether they had an allergic or non‑allergic reaction

  • the drug name and a description of their reaction (see recommendation 1.1.1)

  • the investigations used to confirm or exclude the diagnosis

  • drugs or drug classes to avoid in future

  • any safe alternative drugs that may be used.

1.3.6 Explain to people in whom allergy to a drug or drug class has been excluded by specialist investigation that they can now take this drug or drug class safely and ensure that their medical records are updated.

1.4 Non‑specialist management and referral to specialist services

General

1.4.1 If drug allergy is suspected:

  • consider stopping the drug suspected to have caused the allergic reaction and advising the person to avoid that drug in future

  • treat the symptoms of the acute reaction if needed; send people with severe reactions to hospital

  • document details of the suspected drug allergy in the person's medical records (see recommendations 1.2.3 and 1.2.6)

  • provide the person with information (see section 1.3).

1.4.2 Refer people to a specialist drug allergy service if they have had:

  • a suspected anaphylactic reaction (also see the NICE guideline on anaphylaxis) or

  • a severe non‑immediate cutaneous reaction (for example, drug reaction with eosinophilia and systemic symptoms [DRESS], Stevens–Johnson Syndrome, toxic epidermal necrolysis).

Non‑steroidal anti‑inflammatory drugs (including selective cyclooxygenase 2 inhibitors)

1.4.3 Explain to people with a suspected allergy to a non‑selective non‑steroidal anti‑inflammatory drug (NSAID) (and their family members or carers as appropriate) that in future they need to avoid all non‑selective NSAIDs, including over‑the‑counter preparations.

1.4.4 For people who have had a mild allergic reaction to a non‑selective NSAID but need an anti‑inflammatory:

  • discuss the benefits and risks of selective cyclooxygenase 2 (COX‑2) inhibitors (including the low risk of drug allergy)

  • consider introducing a selective COX‑2 inhibitor at the lowest starting dose with only a single dose on the first day.

1.4.5 Do not offer a selective COX‑2 inhibitor to people in a non‑specialist setting if they have had a severe reaction, such as anaphylaxis, severe angioedema or an asthmatic reaction, to a non‑selective NSAID.

1.4.6 Refer people who need treatment with an NSAID to a specialist drug allergy service if they have had a suspected allergic reaction to an NSAID with symptoms such as anaphylaxis, severe angioedema or an asthmatic reaction.

1.4.7 Be aware that people with asthma who also have nasal polyps are likely to have NSAID‑sensitive asthma unless they are known to have tolerated NSAIDs in the last 12 months.

Beta‑lactam antibiotics

1.4.8 Refer people with a suspected allergy to beta‑lactam antibiotics to a specialist drug allergy service if they:

  • need treatment for a disease or condition that can only be treated by a beta‑lactam antibiotic or

  • are likely to need beta‑lactam antibiotics frequently in the future (for example, people with recurrent bacterial infections or immune deficiency).

1.4.9 Consider referring people to a specialist drug allergy service if they are not able to take beta‑lactam antibiotics and at least 1 other class of antibiotic because of suspected allergy to these antibiotics.

Local anaesthetics

1.4.10 Refer people to a specialist drug allergy service if they need a procedure involving a local anaesthetic that they are unable to have because of suspected allergy to local anaesthetics.

General anaesthesia

1.4.11 Refer people to a specialist drug allergy service if they have had anaphylaxis or another suspected allergic reaction during or immediately after general anaesthesia.



[2] Note that these boxes describe common and important presenting features of drug allergy but other presentations are also recognised

  • National Institute for Health and Care Excellence (NICE)