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Seasonal allergic rhinitis and prevalent allergens

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Allergic rhinitis (AR) affects as many as 16 million in SA – which places its reported estimation at higher than confirmed TB and other infectious diseases​. The cost of allergies to the South African economy is more than R606m a year, in terms of healthcare expenditure and lost productivity. Consequences include morbidity, employment absenteeism, school performance and quality of life (QoL).

AR definition

AR manifests as inflammation of the lining of the nose and is accompanied by nasal symptoms including rhinorrhoea, sneezing, nasal congestion, and itching​. It is also often associated with ocular symptoms​.

AR is clinically defined as a symptomatic disorder of the nose induced after allergen exposure by IgE-mediated inflammation. AR is a reaction involving the immune system, to ​things that should be harmless, mostly aeroallergens.

Symptoms

Physical symptoms​ can be debilitating, involving local complications such as otitis media and sinusitis. Atopic complications include asthma worsening. Uncontrolled symptoms can result in poor sleep quality, and emotional and scholastic implications​.

Diagnosis

Diagnose AR aggressively​ and treat according to guidelines. When doing a physical examination, take note of:

  • Nasal mucosa​
  • Oropharynx clear rhinorrhoea
  • Cobble stoning of posterior pharynx​
  • Ears’ retracted drums.

Associated conditions include allergic conjunctivitis​, sinusitis​, atopic dermatitis, asthma​, and oral allergy syndrome​.

Young children can get environmental allergies, especially if there is an atopic/family history​. Testing is accurate from 3-4 months age​. This helps differentiate recurrent infections from allergies​.

Intercurrent infections are one of the most common causes of allergy/asthma flares.

If you are not sure, do allergy tests. Both viral colds and allergies can present with a runny nose, cough, sneezing and red eyes​. Common colds can last up to three weeks, hence they are  easily confused with an ‘allergy’​.

The picture can be even more clouded in young children, who can catch 10-12 colds per year, so are seemingly always sick (‘allergies’)​.

Risk factors

 AR risk factors include:

  • Family history of atopy​
  • Male sex​
  • Birth during pollen season​
  • Firstborn​ child
  • Early antibiotic use​
  • Maternal smoking in infancy​
  • Exposure to indoor allergens.

Allergic rhinitis classification

AR can be classified by aetiology: seasonal or perennial, or by duration of symptoms and severity of symptoms: ​

  • Intermittent​: <4 days per week​, <4 weeks​
  • Persistent: >4 days per week​, and more than for 4 weeks.

Seasonal allergic rhinitis is less common than persistent AR. However, patients may have persistent AR with seasonal worsening. True seasonal AR stems from pollens from trees, weeds and grasses. Symptoms are predictable and reproducible annually. However, patients may experience symptom changes over time​, such as increased sensitivity to allergens over time​ and inflamed mucosa​. A lower dose of allergen is required for degranulation​.

Symptom phases of AR

Symptoms of allergic rhinitis often occur in two phases, early and late. In Phase 1, there is sensitisation to an allergen, causing early inflammation. Phase 2 clinical disease consists of late inflammation, and an overall exaggerated clinical response.

Early-phase symptoms: The early phase occurs within minutes of exposure to the allergen and includes:

  • Runny nose (discharge is usually clear)
  • Frequent or repetitive sneezing
  • Red and watery eyes (allergic conjunctivitis)
  • Itching in the eyes, nose, throat, or roof of the mouth.

Late-phase symptoms: Symptoms that may develop several hours or later after exposure commonly include:

  • Nasal congestion
  • Postnasal drip
  • Frequent throat clearing (usually related to postnasal drip)
  • Blocked ears
  • Physical discomfort and fatigue (common in children).

Causes of seasonal AR ​

Important causes of seasonal AR are wind-pollinated plants, such as grasses, certain trees, and weeds. Generally, the plants with big bright flowers, and even fynbos are not causes, as these tend to be pollinated by insects. The most allergenic pollen in SA comes from the plants that are not indigenous but have been introduced; for example trees like plane and oak from the Northern Hemisphere are extremely allergenic.

Cross-reactive grass pollens are rye, winter​, thatching​, buffalo.

Non-cross-reacting grasses, that need to be tested separately, are kikuyu​, Bermuda.

Pollens to be aware of are those from the following plants.

Trees

Cypress trees (Cupressaceae)

Cypress trees were introduced from Europe. The African species is Widdringtonia from the Cedarberg area. These evergreen trees produce woody cones and release their allergenic pollen from June.

Oak trees (Quercus robur)

Quercus robur is the species of oak tree most found in South Africa. Oak trees produce acorns from late summer then shed their leaves. Allergenic pollen is released in spring.

Plane trees (Platanus acerifolia)

Plane trees, most commonly London plane trees, have a short pollen-release season of six weeks in spring when they flower from the end of August.

Olive trees (Olea europaea)

The wild olive Olea europaea, subspecies Africana is a popular tree that has been planted throughout South Africa especially in public spaces. It releases allergenic pollen from October to March.

Elm trees (Celtis Africana)

Celtis Africana or white stinkwood is an indigenous South African hardwood tree that flowers from October to March releasing allergenic pollen.

Rhus (Searsia)

This indigenous tree is widely planted because it is fast-growing and economical with space. There are 74 species with diverse flowering times, so the allergenic pollen is released from October to March. Although it is insect-pollinated, the pollen is detected in air samples. The sap from this tree may cause contact dermatitis.

Grasses

Ryegrass (Lolium perenne/L. temulentum)

Ryegrass is considered to be extremely allergenic. It flowers in mid-season, from late September.

Winter grass (Poa annua)

This tiny grass flowers in June in winter rainfall areas. It is related to Poa pratensis or Kentucky blue grass and has characteristic crinkled ‘herring bone’ pattern on some of its leaves.

Wild oat grass (Avena fatua/A. barbata)

Wild oat grass appears in midwinter in some areas but takes a few weeks to grow to its maximum height of 1-4 feet before it releases pollen. It produces long waving fronds from August.

Bunny tail grass (Lagurus ovatus)

‘Bunny tail grass’ appears in September-October. It is found in sandy soil but is rarely seen in the heavier soil of the land close to the mountains in the Cape.

Thatching grass (Hyparrhenia hirta)

Thatching grass is very tall and widespread in South Africa but is mostly found in the grassland areas of Gauteng and the Eastern Cape, and releases pollen from September to June.

Bermuda grass (Cynodon dactylon)

Bermuda grass must be tested separately when patients undergo grass sensitivity tests because it does not cross-react as most other grasses do. It grows most happily in sandy soil and releases most pollen in late summer, but it may be seen throughout the year.

Buffalo grass (Stenotaphrum secundatum)

This indigenous African grass is known as buffalo grass and is a coastal grass. It may be seen in the Cape, especially along the east coast and on the Otter Trail between Knysna and Nature’s Valley.

Kikuyu (Pennisetum clandestinum)

The common name for this grass is Kikuyu and it originated in East Africa. It is favoured as a lawn grass. Take care that the nursery is selling the female grass seedlings that do not produce pollen. Like bermuda grass, kikuyu grass allergy must be tested for separately.

Weeds

English Plantain (Plantago lanceolata)

This weed is widespread throughout South Africa and is seen during most months of the year, although its peak flowering season is in December.

Dandelion (Taraxacum officinale)

The dandelion flowers more strongly in summer but it appears throughout the year. Its peak flowering time is late summer-autumn.

Reeds (Restionaceae)

There are numerous species of reeds, and they are found throughout SA. They are happiest growing close to water in rivers or lakes. The different species flower at different times of the year, so that there is Restio pollen in the air all year round.

Daisies/Cosmos (Asteraceae)

There are many species in the Asteraceae family – Spring daisies and Cosmos – and there are few months without cheerful daisies. November and March are the peak months for Cosmos.

Heath (Erica)

Heath are Fynbos plants in the genus Erica. Fynbos are mostly insect-pollinated, but pollen from species of this genus is constantly found from air samples from July until March.

Why should we measure pollen counts?​

Every pollen season is different​. Climate change has affected the pollen count and we have seen an increase in the total pollen count​ as well as in allergenic proteins​. There has been a spread of new allergenic plants into different areas​, as well as an increase in the pollen season length and intensity​. A valuable resource in this regard is the daily pollen count reports on: https://pollencount.co.za/report/

Available treatment

Allergic inflammation can already be in the nose and airways before the patient has symptoms. Allergy medications work best if they are already in the system at the time of allergen exposure. ​

There is a myth that patients will build up a tolerance if using medication. Note that there is a waxing and waning nature of the disease​. There could also be intercurrent infection​ or an increase in allergen exposure. Pattern of exposure determines reactivity.

​Inhaled corticosteroids (ICS) are the safest and most effective means to treat allergic rhinitis and asthma.​ Systemic absorption is minimal if doses are used prudently, and the patient would have to take ICS for several months to have the equivalent steroid exposure to a short course of oral steroids. ​

​Don’t use systemic steroids for uncomplicated allergic rhinitis. In terms of oral antihistamines (OAH), treatment has changed, and first-generation antihistamines are not useful for seasonal AR. Oral antihistamines have an onset of action in over 60 minutes​, with limited benefit to congestion​.

Intranasal antihistamines​ (INAH) have an onset of action minutes​, with greater efficacy on congestion​. Intranasal corticosteroids​ have an onset of action in hours​, with maximum effect in days. They have an inconsistent effect on ocular symptoms​ and no effect on mast cell degranulation​. You ideally want to target more than one cytokine if possible. A single drug class cannot provide overall symptom relief and control.

Focus on intranasal steroids

How do they work? ​Intranasal steroids (INS):

  • Glucocorticoids penetrate plasma membrane​
  • Bind to cytosolic glucocorticoid receptor​
  • Complex translocates into nucleus​
  • Binds to DNA in ‘steroid responsive gene’ regions ​
  • Activate anti-inflammatory genes​
  • Repress pro-inflammatory genes.​

So INS have multiple sites of action​ but take 3-6 hours to start working​, with a maximal effect after 2-4 weeks.

Focus on antihistamines

How do they work? ​

The histamine H4 receptors alternate between active and inactive form​. Histamine preferentially binds and stabilises the active conformation (agonist)​. Antihistamines preferentially bind and stabilise receptor in the inactive form (inverse agonist)​. Antihistamines have multiple antihistamine actions​ but do not act on other cytokines and chemicals​. There is a rapid onset of action – within 5-15 minutes.​ Local antihistamines act even faster and circumvent systemic side effects .

Combination INCS and INAH​

 The benefits of combining INCS and INAH:

  • Rapid symptom control​
  • Combination spray theoretical decreased run off anteriorly and posteriorly​
  • Possible better adherence with combination therapy​
  • Reliever and controller combination​.

Over 70% of patients with moderate to severe AR require multiple therapies to achieve effective symptom relief.

Conclusion

Seasonal allergies are increasing​ and have a significant effect on quality of life​. Take a diagnostic approach ​and use the appropriate pollen calendar to guide testing​. Treatment has changed.

References available on request.

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