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Allergy friendly plants – indoors and outdoors

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Plants and flowers have a positive effect on people’s quality of life – in contrast to a sterile environment. Because of their importance to human life, plants must be carefully chosen to be tolerated by most people, including those with allergies and other sensitivities. This is especially important for public institutions such as schools, kindergartens, hospitals, town halls and shopping centers.

How can plants cause health problems?

Pollen allergy is an allergic reaction to tiny particles (pollen) released from plants. Pollen is produced by male reproductive structures. It is primarily wind-pollinated plants that cause pollen allergy – such as trees, weeds or grass. Common allergic symptoms are nasal congestion, an itchy nose, watery eyes, coughing and shortness of breath.

Fragrance from plants may be an irritant to people who are sensitive to certain odors, so called fragrance hypersensitivity. Hypersensitivity can exist without the person concerned being allergic; without the body reacting by releasing adverse antibodies and accordingly allergy tests would show no results. Tolerance in allergic individuals is however often reduced.

Human perception of fragrance varies enormously from person to person. A fragrance which is enticing to one person can be repulsive to another, or you may be simply unable to detect any fragrance at all in a flower which someone else finds strongly aromatic.

Plant dermatitis is caused by reaction to skin contact with certain plants. It is not always obvious which plant is responsible for a flare-up of the dermatitis (also known as eczema). Irritant contact dermatitis arises in those with sensitive skin, if they've handled the plants too much, or if the plants have prickles or barbs. Other plants cause a rash only in certain people who have developed an allergy to them, i.e. allergic contact dermatitis. It is also possible to get rash from pollen carried in the wind.

Cross reactions. Most of the non-food related allergies can be accompanied by reactions in the mouth or the gastrointestinal tract. The reason for the cross-reactions lies in the structural similarities among proteins of diverse sources, such as pollens and foods. For example, individuals who react to pollen from birch trees commonly react to apple, carrot, celery, pear, tomato, cherry and tree nuts.

Toxic reactions occur following ingestion of a poisonous part of a plant. There are thousands of poisonous plants, and numerous variations of toxins. Nevertheless, acute poisoning is very rare. Poison generally occurs at lower concentrations in plants, or the fragrance or taste of the plants are repellent – hence people avoid contact with them.

What should you think about when selecting plants?

Avoid plants that produce pollen in significant quantities.

Reduce male flowers. Ask your local garden-center expert for help. You can also aim for so called perfect flowers, which means they contain both male and female parts; as a result, the pollen doesn't have to travel far and are hence less likely to cause pollen allergy. Sometimes you can also get female clones of diecious species.

Choose insect-pollinated plants rather than wind-pollinated plants. Unfortunately, highly susceptible people may be affected by some insect-pollinated plants as well. Some insect-pollinated plants do, however, produce pollen in large amounts that could be enough to cause allergic reactions, such as Salix.

Avoid fragrant plants – particularly for indoor.

See list and illustrations of allergy friendly plants