If you suffer from an allergy, you are hypersensitive to particular substances. There are various forms of allergies, all dependent on the substance(s) you are allergic to. For instance, you might be allergic to the droppings of the house dust mite, to mycotoxins and mould spores, or to the toxic emissions that are caused by the chemical breakdown of building materials. These are all types that are directly or indirectly linked to excessive humidity at home. For example, an allergy can cause nasal catarrh (blocked nose, runny nose, constant sneezing) or an asthmatic cough. A particular type of allergy is towards silverfish. Silverfish occur in damp places, such as the corners of kitchen cabinets, behind the kitchen units and in wet paper. If you suffer from this type of allergy, you might have symptoms similar to asthma such as tightness in the chest. .

As opposed to ordinary rhinitis or hay-fever, which is caused by air-borne pollen, the chronic form of it is caused by a badly ventilated environment and/or excessive damp which in turn causes mould and the house dust mite. The disorder is an inflammation of the nasal mucous membrane, caused by a virus, a parasite or an external bacteria. Chronic rhinitis causes coughing, tiredness, headache, irritation of the eyes and runny noses.

Asthma is an inflammation of the airways. Symptoms may be: wheezing, shortness of breath, a tight chest and coughing. For many people one of the causes of asthma is an allergic reaction. The main allergic triggers are pollen and the house dust mite, the little creature that feels most at home in warm and damp houses.

Eczema is a skin reaction which causes inflammation. One of the main causes of this is the house dust mite which is common in damp houses. So people who suffer from eczema would benefit from getting the correct relative humidity in their homes. It should neither be too high nor too low. Excessively low humidity may increase the symptoms in the form of dry eczema so a balance is important.

During the building of a house spores of mould regularly stay behind in the walls and floors. These are so-called ‘black moulds’. In normal circumstances, this is not a problem, as long as the house is kept in a dry condition and is well ventilated. But when there is high humidity or any ingress of water from flood or leakages, these dormant spores suddenly become very active. They multiply and start to grow considerably. Multiplication of black mould takes place via spores which contain harmful chemical agents. These spores will become air-borne and will nestle in all kinds of things in your home. If these spores come into contact with the skin it will cause small wounds and irritation. If you breathe in these spores, the chemical agents will end up in your lungs where they will nestle in small air sacks. The resulting inflammation can cause laboured and painful breathing. Swallowing these spores, because they end up on food for example, may cause inflammation of the bowel and stomach. Ultimately, the spores will find their way to the network of blood vessels that supply our brain. This will delay the blood circulation. They may also damage the nervous system. In particular the disturbance of the exchange of brain signals and with that also the sensory, thinking and motor functions.

More formaldehyde is being released from board materials such as chipboard, multiplex and even curtain fabrics in an excessively damp environment. Formaldehyde is a colourless gas with a prickly, sharp smell. Formaldehyde does not just originate from new materials but it can be released for many years. The warmer and damper the board material is, the more formaldehyde it releases. If formaldehyde is air-borne, it may irritate the nose, throat and eyes. People with sensitive airways will definitely notice the adverse effects. Some people can develop a hypersensitivity when they come into contact with this irritating gas. Ultimately, this will result in asthma-like symptoms. Contact with the skin may result in eczema. Therefore never use chipboard in a warm and damp environment, such as a bathroom or behind radiators. Always tape over unfinished seams with foil, veneer or aluminium tape and finish unfinished plates of chipboard with paint or lacquer. Always look out for the KOMO-certification. Chipboard with this certification contains a very small amount of formaldehyde.