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Useful facts on allergy-friendly house and garden plants (allergivennlige inne- og uteplanter)

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Everyone should be able to surround themselves with plants.

Allergic individuals may, understandably, be tempted to feel that their home, surroundings and workplace, should be completely plant-free, in order to stay on the safe side in terms of possible health problems. Such a choice involves the individual relinquishing an important general dimension of existence – since closeness to nature and plant life is essential for our quality of life. Clear psychological and physical health benefits have been demonstrated by individuals being able to live within a green environment – in contrast to a sterile environment. Public spaces must also, as far as possible, be accessible to allergic individuals and those with other hypersensitivity reactions. Those responsible for horticultural landscaping around and inside institutions such as schools, kindergartens, nursing homes, hospitals, service offices, shopping centres, etc., have a particular responsibility in this respect.

What health problems can plants cause?

Pollen allergy is a widespread and well-known term. It received the name “pollen allergy” because the pollen grains are carriers of the allergens which trigger reactions. The pollen grains get “the blame” because they are carriers of the allergens which cause reactions. In allergy-provoking plants the concentration is particularly strong in the pollen vector, hence the reaction is named after the latter. The allergens are however also found in other parts of plants, particularly in the foliage. Individuals allergic to grass pollens notice this particularly when they mow lawns, even though flowering grass is not in the immediate vicinity. (See Useful facts on pollen allergy).

Fragrance hypersensitivity means hypersensitivity to plant fragrances and is quite common. It is important to understand that such hypersensitivity can exist without the person concerned being allergic; without the body reacting by the release of adverse antibodies and accordingly without the allergy tests resulting in a reaction. Tolerance in allergic individuals is however often reduced. The mucosa is already affected by one or other allergy, and then the symptoms become noticeable at lower concentrations of the fragrances.

Skin reactions:

When the skin comes into contact with plants, symptoms can occur at the contact site. However the substances can also be inhaled and spread via the circulation, and cause symptoms in completely different parts of the body. Reactions may also occur on contact with microparticles which plants release to the air. (See Useful facts on eczema).

Food reactions following ingestion of vegetables may be due to several factors. It is usual to differentiate between reactions which are immunological (food allergy) and non-immunological (food intolerance). It is these allergic reactions which are the most serious, and they can be triggered by minimal quantities of the allergen. (See Useful facts on food allergy).

Cross-reactions.

Many individuals who react to pollen from birch trees also react to a number of other plants, fruits and vegetables, e.g. individuals sensitive to the Weeping fig will easily develop latex allergy. This is an expression of so-called cross-allergy. The immune system does not differentiate between allergens from birch and allergens from stone-fruits and certain other foodstuffs.

(See Useful facts on cross-reactions).  

Toxic reactions

The term “poisonous plants” is understood to mean plants containing substances which can have harmful effects. This may occur via the mucosa in the eye, nose and airway, the skin, in the gut or elsewhere in the organism following ingestion of the poison. There are thousands of poisonous plants, and numerous variations of toxins. Nevertheless, acute poisoning is very rare. This is due to the fact that the poison generally occurs at lower concentrations in the plant, or that the fragrance or taste is repellent – hence people avoid contact with it.

Which plants are good choices?

In this context plants are divided into three groups, with clear “yes” plants on the one side and clear “no” plants on the other – and with a varied grey-zone group in the middle. In terms of choice of indoor plants, there is a much more restricted choice of recommended plants than for outside plants, where air exchange and the conditions are generally significantly different, and tolerance in relation to fragrance problems, etc., is higher. We include some examples of good plant choices:

Outdoor plants

Trees:

Azaleas (Sorbus intermedia), Blue spruce (Picea pungens), Norwegian maple (Acer), Larch (Larix), Rowan (Sorbus), Thuja (Thuja).

Bushes:

Hawthorn species (Crataegus), Dogwood species (Cornus), Cinquefoil (Potentilla), Cotoneaster species (Cotoneaster) and unscented roses (Roses).

Climbing plants:

Aralia (Hedera helix), hops (Humulus), Clematis (Clematis).

Perennials:

Columbine (Aquilegia vulgaris), White stonecrop (Sedum), violet species (Viola), Meadow rue (Thalictrum), Mallow species (Malva), Bleeding heart (Dicentra spectabilis), Lady’s mantle (Alchemilla), Larkspur (Delphinium), Poppy species (Papaver).

Indoor plants

Busy Lizzie (Impatiens), spider plants (Chlorophytum), palm-species (Arecaceae), Fuschia species (Fuchsia), Mimulus (Mimulus), Baby’s tears (Soleirolia), Flaming Katy (Kalanchoë), Four O’clock (Hibiscus), Hydrangea (Hydrangea), Phyllocladium (Cactaceae), China Doll (Radermachera),  Erica (Erica), Golden pothos (Philodendron), Silver pothos (Scindapsus pictus) and orchids (Orchidaceae) – and unscented rose (Rosa) species.

What sources of information are there?

Friendly and unfriendly plants in our near environment (revised edition 2000) is a lexical reference book which includes approximately 1,000 species of indoor and outdoor plants and their potential effects on health. Good advice is green (2005) gives advice and suggestions for comprehensive solutions for a safe green environment for all, for both private and public areas, and with accompanying plant lists. Both books have been published by a special publishing house for Sør-Trøndelag County Municipality by NAAF (www.naafstrl.no) and may be ordered here. For poisonous plants, the Directorate of Health and Social Affairs has issued a series of brochures in the series Children and poisoning, e.g. Wild plants – are they dangerous? These are available in most pharmacists throughout the country.