Allergy clinics are gradually resuming activity, but there are still many patients on waiting lists for diagnostic tests.
This article suggests interventions for the more common allergy presentations.
Hayfever
Patients with severe symptoms should be advised to use a topical nasal steroid regularly, in addition to a long-acting, non-sedating antihistamine.1 Pre-treating with isotonic saline douche 20 minutes before the nasal spray clears passages so topical treatment is more effective.
If very congested, patients can use a decongestant spray such as xylometazoline alongside the nasal steroid, for a maximum of three days. Those with prominent eye symptoms should use anti-allergic eye drops.
hayfever
hayfever
The cost of medications over the counter may be prohibitive, especially in a prolonged season. For patients who pay for prescriptions, a prepayment certificate may reduce costs.2
Patients with significant concurrent pollen asthma should be started on a preventer inhaler during the season, in accordance with BTS/SIGN guidelines.3 Consider a short course of oral steroids to initiate rapid control of very severe symptoms – this will not cause immunosuppression significant enough to require shielding from Covid-19.
Topical nasal steroids work best if started early in the season, before the inflammatory infiltrate has accumulated. Reliance on antihistamines often results in poor symptom control as these do not control the inflammation. The newer topical steroids have greater potency and minimal systemic absorption compared with beclomethasone and are preferable when hayfever is difficult to control. Systemic absorption of topical steroid is undesirable, particularly in children.
A combination of topical steroid with topical antihistamine is a good option.
Patients may be reluctant to start topical nasal steroids because of undue worries about systemic side-effects. Local septal crusting or bleeding can be minimised by aiming the spray away from the septum and applying petroleum jelly to the septum.
The same treatments can be safely administered continually for perennial allergic rhinitis. Consider possible occupational and domestic triggers. These will require diagnostic testing in due course.
Anosmia in the context of perennial rhinitis usually suggests polyps, but a patient with new-onset anosmia should be assessed for Covid-19 and advised to self-isolate. Anosmia due to polyps may resolve with topical steroid treatment but if persistent, refer for ENT assessment.
A short course of oral prednisolone may control symptoms if polyps are not extensive, but the topical steroid will need to be continued.
Acute urticaria
Acute urticaria causes a lot of confusion. It is often triggered by intercurrent infection and typically lasts less than six weeks.4 Enquire about infections and any medications such as NSAIDs that could be the cause. Food allergy is unlikely unless the response occurs within a few minutes to an hour of ingestion and is shortlived. Treat with long-acting non-sedating antihistamines as needed or as for chronic urticaria.
Chronic urticaria
Most patients seen in allergy clinics with chronic urticaria have non-allergic, spontaneous urticaria. Spontaneous urticaria looks identical to allergic urticaria and patients are often anxious about a possible allergy. Explain that while the rash is identical, it is caused by histamine-releasing autoimmune mechanisms that usually burn out over time, with no damage to skin or immune system. By contrast, with a food allergy, there is a close association with ingestion of a specific food, usually within an hour and with symptoms inside the mouth. Food allergy symptoms also generally abate within a few hours and do not recur randomly. Urticaria can be distressing and the concept of autoimmunity can be difficult to grasp, so it can be hard to reassure patients. Referral may still be necessary.
Urticaria can be associated with angioedema
Start a daily dose of long-acting non-sedating antihistamine, such as cetirizine or loratadine, and escalate to up to four times the recommended daily dose, as needed. Higher than formulary doses are often needed to achieve control as recommended in British Society of Allergy and Clinical Immunology (BSACI) guidelines.5 Montelukast can also be added.
Symptoms can be difficult to control; short courses of prednisolone might be needed while waiting to refer to a centre offering immunosuppressants or anti-IgE. Urticaria is commonly associated with thyroid disorders, so investigate this when possible. Tests should include full blood count to check for eosinophilia and iron deficiency, thyroid function test, thyroid peroxidase and anti-nuclear antibodies (ANA) if other autoimmunity is suspected. If there are significant abnormalities, refer to the appropriate specialist.
Dealing with anaphylaxis during lockdown
Anaphylaxis is defined as a severe, life-threatening, generalised or systemic hypersensitivity reaction. It is characterised by rapidly developing life-threatening airway, breathing or circulation problems, and usually (but not always) skin and mucosal changes.8
Refer any patient who has been treated in A&E with suspected anaphylaxis urgently to an allergy clinic. Even if the patient self-managed, referral is advisable.
Provide as much information as possible in the referral about the ingredients of food eaten in the two hours before onset, the timing and symptoms of the reaction, observations recorded and any potential medication cause or co-factor. It may be possible for the clinic to arrange skin and blood testing before remote consultation, reducing potential patient and staff exposure to Covid-19.
Those at risk from unexpected allergen exposure (primary food allergy or systemic reaction to insect venom), or those with airway angioedema or possible idiopathic anaphylaxis should be prescribed two adrenaline autoinjectors (AAIs), in accordance with MHRA advice.
Patients with local reactions to insect stings, non-anaphylactic pollen food syndrome, probable spontaneous urticaria or symptoms suggesting low likelihood of food allergy do not need to carry an AAI. However, provision of an AAI may sometimes be necessary as an interim measure if there is uncertain anaphylactic risk, particularly in asthmatics who are at higher risk from food reactions, while awaiting formal risk assessment.
Advise patients on using the devices, directing them to the Anaphylaxis Campaign website for support and the manufacturer’s website for instructions and demonstrator pens.
Advise patients on indications for use – principally for breathing difficulties or faintness during an allergic reaction.
Emphasise that antihistamines do not work quickly so the AAI should be used immediately and an ambulance called straight away.
Although patients might be concerned about attending A&E at this time, it is vital they seek emergency treatment – anaphylaxis cannot be managed safely in the community.
Skin conditions
Rashes that do not look urticarial should be referred for a dermatological opinion.
eczema on hand square PPL
eczema on hand square PPL
While eczema can be associated with IgE-mediated allergy, if the condition is well managed, concerns about food triggers should diminish. Remember that eczema is associated with a high total IgE, which can interfere with IgE tests leading to false positive results. Unless there are immediate food allergic reactions, such testing is best avoided.
In infants with severe treatment-resistant eczema, consider cow’s milk allergy. Refer to the iMAP guideline but ensure close supervision, preferably by a dietitian, as overdiagnosis is a risk.6
If urticarial lesions last longer than 48 hours and leave bruising or staining, consider vasculitis. If eczematous changes are present, consider a contact allergen, up to three days before onset. These patients may need to see a dermatologist.
Angioedema
Urticaria can be associated with angioedema. If there is airway compromise, prescribe autoinjectors (see box, above). Urticaria with angioedema should respond to treatment for urticaria alone, but may take longer to resolve.
The angioedema should be investigated for C1 inhibitor deficiency and this will usually need referral. Request an urgent assessment if severe, frequent or worsening. As C1 inhibitor deficiency is rare, investigation should include the usual tests done for urticaria but also immunoglobulin screen and protein electrophoresis in older patients to exclude paraproteinaemia.
Angioedema can be an adverse reaction to ACE inhibitors. It can begin after years of use. ACE inhibitors should be avoided in angioedema and patients must be switched to an alternative class of drug. This can include angiotensin receptor blockers (ARBs). Symptoms from the ACE inhibitor may recur after switching medication. ARBs should be stopped if frequent, moderate-to-severe symptoms or airway symptoms persist.
Suspected food allergy
Patients often attribute symptoms to food allergy. GI symptoms in isolation, fatigue, headaches and nonspecific complexes of symptoms are unlikely to be allergic. Refer to the appropriate specialist in due course.
Food allergy is highly likely where the patient experiences itch, tingling or swelling in the mouth or throat within a few minutes of eating, especially if there are repeated episodes with the same foods and with common allergens such as nuts, seeds, fish, seafood, dairy, egg, wheat or soya.
nuts
nuts
The patient may be convinced they know what caused their symptoms and miss another cause. Ask about everything ingested in the two hours before onset, including food, drink, supplements and drugs, and any medications taken that day. Consider pollen food syndrome if an oral reaction only happens with raw fruit, raw vegetables or raw nuts. With this, the reaction is usually limited in severity as the allergens break down on digestion, but around 2% of patients develop anaphylaxis.
Food allergens that are primary sensitisers are usually stable to heat and digestion and have the greatest potential for provoking anaphylaxis. Examples include nut, seed and legume (major storage proteins), seafood proteins, casein in dairy and the egg white allergen ovomucoid. Processed foods and composite meals increasingly contain unexpected ingredients, making it difficult to identify a trigger. In this case patients will need diagnostic testing, but in the meantime suggest they record ingredients. If a food contains a common allergen such as nuts, advise they avoid it while awaiting confirmation, unless it has been eaten safely since.
Patient leaflets on the Anaphylaxis Campaign website can help identify food allergens.7
Co-factor dependent food allergy
Certain co-factors – including exercise and NSAIDs – can trigger a delayed reaction to foods such as wheat or crustaceans. The reaction usually occurs within two hours of eating. Co-factors can also trigger reactions in lipid transfer protein (LTP) food allergy syndrome – where patients react to LTP allergen in fruit (especially stone fruit), vegetables, nuts and grain. Only those LTP allergen-containing foods that have provoked a reaction need be avoided but remember that, in contrast with pollen food syndrome, LTP allergen is not destroyed by cooking. LTP food allergy requires specialist input.
Patients with a clear exercise trigger should be advised to avoid even minor exercise within two hours after eating. NSAIDs are best avoided altogether. An anaphylaxis kit is also advisable as other co-factors can be involved – such as stress, infection, alcohol, fasting and premenstrual phase. These patients can have varied and complex presentations and must be referred. If there are acute severe reactions, you may need to arrange an urgent teleconsultation.
Allergic asthma
It is vital for asthma to be well controlled so it is not an extra risk for respiratory complications with Covid-19.9,10
Asthma must also be well controlled in patients at anaphylactic risk: uncontrolled asthma can complicate an anaphylactic reaction, making it more resistant to treatment.
Patients with severe asthma should continue to be monitored by a respiratory clinic. If you suspect allergic triggers in the home or at work, the patient may need allergy investigation. Domestic exposure can be assessed by IgE testing, but it is possible to be sensitised and not clinically reactive. If symptoms are provoked within minutes of contact with dust or a pet, consider avoidance measures. If an occupational trigger is suspected, refer to occupational health to consider whether redeployment is indicated or seek advice from a chest clinic.
Dr Cecilia Trigg is a consultant allergist at St Mary’s Hospital in London
References
1 Scadding G, Kariyawasam H, Scadding G et al. BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis. Clin Exp Allergy 2017;47: 856-9
2 UK Government. Get a prescription prepayment certificate. gov.uk/get-a-ppc
3 BTS/SIGN Guidelines 158 British guideline on the management of asthma. July 2019. tinyurl.com/SIGN-asthma
4 NICE. Clinical Knowledge Summary. Urticaria: Diagnosis. Last revised January 2018 cks.nice.org.uk/urticaria
5 Powell R, Leech S, Till S et al. BSACI guideline for the management of chronic urticaria and angioedema. Clin Exp Allergy 2015;45 547-65
6 Venter C, Brown T, Meyer R et al. Better recognition, diagnosis and management of non-IgE-mediated cow’s milk allergy in infancy: iMAP—an international interpretation of the MAP (Milk Allergy in Primary Care) guideline. Clin Transl Allergy 2017; 7: 26
7 Anaphylaxis Campaign. Factsheets. tinyurl.com/anaphylaxis-factsheets
8 UK Resuscitation Council. Anaphylaxis. resus.org.uk/anaphylaxis/
9 NICE. COVID-19 rapid guideline: severe asthma. April 2020. https://www.nice.org.uk/guidance/ng166
10 Primary Care Respiratory Society. PCRS pragmatic guidance. Diagnosing and managing asthma attacks and people with COPD presenting in crisis during the UK Covid 19 epidemic. May 2020
