Summer time is coming to an end- allergies caused by grass and tree pollens are easing off- but with a new season comes a new set of prevailing allergens. “Winter –related” allergies can be mediated in 3 ways:
- exposure to those allergens which are more prolific during the winter months leading to typical allergic rhinitis or asthma
- worsening of allergies and asthma secondary to winter viruses
- worsening of symptoms because of the cold air itself.
Allergens which are more prolific during the winter months
The bulk of allergens which have higher levels during winter are indoor allergens, including house dust mite, moulds, cockroaches and pet dander. 1 The reason for an increased exposure to such allergens during winter months is a reduction in indoor ventilation and an associated increase in indoor humidity levels, and a greater amount of time spent indoors in contact with such allergens.
Those with an allergy to pet dander can have symptoms all year round, but winter may be associated with more flare ups than usual. Reduced ventilation in the home (less open windows and doors), as well as increased time spent by pets indoors during winter, may contribute. Patients with a pet dander allergy should take the following steps during winter:2
- Vacuum regularly using a vacuum cleaner with a HEPA filter (high efficiency particulate air filter)
- Discourage dogs from sleeping in bedrooms and on couches.
- Dogs should be groomed and washed regularly, but not inside the house.
House dust mites are perennial allergens but exposure levels do tend to peak over winter time with reduced household ventilation and increased time spent indoors. Fluffy blankets, down duvets and thick coats which have been taken out of storage cupboards all trap house dust mite too, hence increasing exposure even more during winter time. During the winter, those suffering from a house dust mite allergy should take the following steps to reduce allergen exposure: 3-5
- Vacuum regularly using a vacuum cleaner with a HEPA filter.
- Reduce fluffy toys and blankets. Wash bedding and blankets at 60 degrees or higher, if possible. Air thick blankets and duvets outside on a sunny day. Fluffy toys and blankets can also be placed in the freezer overnight then washed at normal temperature to reduce dust mite carriage.
- Wet-mop floors instead of sweeping, especially in bedrooms
- Consider use of house dust mite impermeable mattress covers, pillow covers and duvet encasings.
Mould thrives in warm, damp regions and is prolific in coastal areas, both inside the house and outside in the garden. Like dust mite it is a perennial allergen, but with reduced household ventilation during winter, excess mould can grow in bathrooms, kitchens and cupboards during winter months. Some tips for reducing mould allergen levels in the house during winter include:6
- Ventilate the house daily, even if the air is a little cold.
- Limit indoor plants and firewood as they can encourage mould proliferation.
- As much as possible avoid hanging wet washing inside the house.
Cockroach droppings can cause allergic symptoms and levels may increase during winter. Inhalation of cockroach droppings can worsen allergic rhinitis and asthma. 7 Cockroach levels can be reduced by keeping food well contained and cleaning up crumbs diligently. Fixing leaky pipes and sealing cracks in the home can also help.
Worsening of allergies due to winter viruses
Cold and flu viruses, which are prolific during winter, can mimic allergic symptoms and simultaneously exacerbate rhinitis and chest symptoms. Pre-existing allergies can, in turn, also lead to prolongation of cold and flu symptoms. Frequent use of nasal saline rinses and diligent use of allergic rhinitis and asthma control treatment such as intranasal /inhaled corticosteroids can lessen the impact of viral illnesses.
Worsening of allergic symptoms because of the cold air itself
Cold-induced airway irritation or damage can cause rhinorrhea or bronchospasm. This is worsened by rapid decreases in temperature and is particularly manifest during exercise in cold weather, when the normal compensatory nasal humidification is bypassed during exercise-induced hyperventilation. 8
Further factors such as an increase in use of indoor fires, higher pollution production, increased use of air-drying indoor heaters can all worsen respiratory allergies.
Winter carries several risk factors for an exacerbation in respiratory allergies. Patients and healthcare providers should ensure that allergic rhinitis and asthma medication plans are up to date and being adhered to, and that indoor allergen exposure is reduced as much as possible during winter time. Additional measures such as frequent use of saline sprays may be helpful in counteracting the drying effects of indoor heaters, and also in reducing the impact of upper respiratory viruses.
- Matsui EC, Abramson SL, Sandel MT. Indoor environmental control practices and asthma management. Pediatrics 2016;138(5)
- Konradsen JR, Fujisawa T, Van Hage M, Hedlin G, et al. Allergy to furry animals: New insights, diagnostic approaches, and challenges. J Allergy Clin Immunol 2015;135(3):616–25.
- Sánchez-Borges M, Fernandez-Caldas E, Thomas WR, Chapman MD, et al. International consensus (ICON) on: Clinical consequences of mite hypersensitivity, a global problem. World Allergy Organ J 2017;10(1):1–26.
- Coopasamy K, Goldstone E, Masekela R. House-dust mites impact disease expression in children with chronic rhinitis: A retrospective study. Curr Allergy Clin Immunol 2017;30(4):258–63.
- Wilson JM, Platts-Mills TAE. Home environmental interventions for house dust mite. J Allergy Clin Immunol Pract 2018;6(1):1–7.
- Ahluwalia SK, Matsui EC, Bethesda MHS. Indoor environmental interventions for furry pet allergens, pest allergens and Mold : Looking to the Future. J Allergy Clin Immunol Pract 2018;6(1):9–19.
- Seedat RY, Claassen J, Claassen AJ, Joubert G. Mite and cockroach sensitisation in patients with allergic rhinitis in the Free State. S Afr Med J 2010;100(3):160–3.
- D’Amato M, Molino A, Calabrese G et al. The impact of cold on the respiratory tract and its consequences to respiratory health. Clinical and translational allergy 2018; 8: 20.