Allergies: not to be sneezed at

The human body responds to foreign substances and objects in many ways. A typical reaction is to develop an allergic response. This happens when our immune system reacts to an allergen as if it were harmful. Of the many allergic reactions, allergic rhinitis and skin allergies are some of the most common and are the focus of this review. A severe allergic reaction is called anaphylaxis, and while relatively rare, it can be serious and even life-threatening.

Allergic rhinitis is a condition that causes fitful sneezing, nasal itching and a stuffy nose. It is estimated to affect about one in every five people in Ireland.

It occurs when the immune system produces antibodies against airborne substances such as dust, mould, pollen and smoke.

It is characterised by an inflammation of the nasal mucus membranes, which happens when the cells in the nose and surrounding tissues release histamine and other chemicals.

Hay fever is a seasonal type of allergic rhinitis caused by a reaction to high concentrations of pollen and grasses, and occurs most frequently in spring and summer.

Hay fever usually affects children from the age of seven; older children and teenagers are more susceptible to the allergy than adults.

Skin allergies are also common. Also known as urticaria – the result of the release of histamines into the skin – the resultant hives can happen as a reaction to certain foods, infections or chemicals.

Other possible causes include food colourants, insect bites, medication and infections.

Most skin allergies are acute and settle in the short term. However, some people may develop chronic urticaria.

Eczema is a form of skin allergy. It affects one in five infants but only about one in 50 adults. It is thought to be due to “leakiness” of the skin barrier, which causes it to dry out and become prone to irritation and inflammation by many environmental factors. Some people with eczema have a food sensitivity which can make eczema symptoms worse.

CAUSES, SIGNS AND SYMPTOMS

Allergic rhinitis is caused by an allergen, such as pollen, dust, mould or flakes of skin from certain animals, leading to inflammation of the lining on the inside of the nose.

As well as sneezing and a stuffy nose, sufferers may experience a postnasal drip, watery eyes and pain around the nasal sinuses.

Hay fever symptoms in children may appear any time from March to October. Sometimes hay fever can be confused with a virus. The way to tell the difference is by how long the symptoms last. If it’s a virus, they should only last for a week or two. If your child has a constant runny nose and is sneezing every day for part of the year but not in the winter, it’s a sign they may be allergic to something.

Most people with allergic rhinitis have mild symptoms that can be easily and effectively treated. However, for some, symptoms can be severe and persistent, causing sleep problems and interfering with everyday life. Seasonal allergic rhinitis can be very disruptive for students sitting summer exams.

The symptoms of allergic rhinitis do occasionally improve with time, but this can take many years and it is unlikely the condition will ever disappear completely.

Your GP will usually be able to diagnose allergic rhinitis based on your symptoms and any possible triggers you may have noticed. If the exact cause of your allergic rhinitis is uncertain, you may be referred for allergy testing.

Skin allergy is caused by the release of histamine into the skin as a result of contact with an allergen or in some cases due to the ingestion of a food colourant or a drug.

The resulting rash usually appears as raised, itchy lumps and tends to come on without warning. The lumps or weals can appear anywhere on the body including the soles of the feet and the palms. They tend to have pale centres and red margins and can spread, joining up to form very large irregular patches.

The diagnosis can usually be made on the basis of the person’s symptoms and the clinical signs. Sometimes, an allergy test called patch testing will be needed to ascertain the exact cause – a small amount of suspected allergens are placed on the skin and looked at some 48 hours later to see which one has caused a mini skin reaction.

Skin allergies are especially common in healthcare settings. Both patients and nurses can develop an allergy to latex, which is a milky liquid found in rubber trees. The resulting rashes include irritant contact dermatitis – where dry, irritated areas of skin occur, typically on the hand. This is not really an allergic reaction but rather an irritation from wearing latex gloves or a reaction to the powder often found inside them.

PREVENTION AND TREATMENT

Allergic rhinitis: If your condition is mild, you can also help reduce the symptoms yourself by taking over-the-counter medications – such as non-sedating antihistamines or decongestants – and by regularly rinsing your nasal passages with salt-water solution to keep your nose free of irritants. Eye drops are also useful.

Seek medical advice if you have tried these self-help measures and they haven’t helped. Your GP may choose to prescribe a stronger medication, such as a nasal spray containing steroids.

With prolonged or constant use, nasal sprays can lose their effectiveness. Initially, the sprays shrink the nasal lining, giving relief to the worst of the symptoms. Over time, however, the mucous membranes react by swelling even more than before, setting up a vicious cycle.

Pollen is released in the early morning. As the air warms up, the pollen is carried up above our heads. As evening comes and the air cools, pollen comes back down.

This means that symptoms of seasonal rhinitis are usually worse first thing in the morning and early evening, particularly on days that have been warm and sunny.

To reduce your child’s exposure to pollens, the following may help: Keep windows closed at night so pollen doesn’t enter the house. Buy your child a pair of wraparound sunglasses to stop pollen entering their eyes. Smear petroleum jelly (Vaseline) around the inside of your child’s nose to trap pollen and stop it being inhaled. Wash your child’s hair, face and hands when they come back indoors, and change their clothes. Don’t let them play in fields or large areas of grassland. Use air filters to try to reduce pollen that’s floating around the house. Keep the car windows shut when driving.

In a minority of cases, allergic rhinitis can lead to complications. These include: nasal polyps – abnormal but benign (non-cancerous) sacs of fluid that grow inside the nasal passages and sinuses; sinusitis – an infection caused by nasal inflammation and swelling that prevents mucus draining from the sinuses; and middle-ear infections – infection of part of the ear located directly behind the eardrum. Skin allergy: Calamine lotion applied to the rash is soothing. Cold compresses can reduce the duration of an acute episode. Your doctor may prescribe antihistamine tablets to relieve the itch and help dampen down the rash.

The itch of eczema is not caused by histamine so antihistamine treatment may not be helpful.

With skin allergies, prevention is most definitely better than cure. For healthcare workers, this may have implications for their livelihoods.

For those working in industry, it is usually possible to either change the chemical causing the problem or to remove the employee from the zone of exposure.

Dr Muiris Houston is a specialist in general practice and occupational medicine and a medical education consultant