They do not always completely control the allergic reaction however, because they do not counteract other chemicals that may be responsible for the symptoms. As the older type of antihistamines result in relaxation and help sleeping, they can be useful in other itchy skin diseases such as eczema, particularly taken at night. They are not thought to be addictive. Conventional antihistamines Conventional antihistamines are obtainable in New Zealand without prescription. It is best not to drink alcohol when taking antihistamines, because this combination could result in excessive and potentially dangerous drowsiness.
Care needs to be taken with antihistamines when driving, flying or underwater diving.
Because they are broken down by the liver, those with liver disease are best to take a reduced dose as there will be excessive levels circulating in the blood stream. In general, all drugs are best avoided in pregnancy, but there is no data to suggest that antihistamines are harmful to the mother or foetus so they are sometimes prescribed for severe urticaria in pregnant women. If a mother is breastfeeding, antihistamines may reduce milk production and could result in drowsiness of the infant, so are best avoided. Unfortunately, antihistamine creams can occasionally cause contact allergic dermatitis so they should not be applied to large areas, and should be discontinued if they result in a rash. They should be avoided on broken skin.