NYDA^® combats head lice by penetrating into and occluding their respiratory openings. The head lice ultimately suffocate. Since water has a higher surface tension than NYDA^®, it is not able to penetrate the respiratory system of the head lice. If NYDA^® is applied to wet hair, the product dilutes and its effect can no longer unfold. This prevents successful treatment.

NYDA^® is free of neurotoxic insecticides, i.e., it does not contain any neurotoxins. The 2-step NYDA^® dimethicone penetrates deep into the respiratory openings and suffocates lice, larvae and nits. This way, the process of diffusion of the parasites is effectively interrupted.

NYDA^® is suitable for all ages including infants.

There is a possibility that the colour of coloured hair may change or that the durability of the colour may be shortened. However, since the introduction of the product in 2006, no problems have been reported in connection with coloured hair. To be safe, you should wait up to 2 days after treatment if you want to colour your hair again. The main components NYDA^® should be washed out by then.

The dimethicone contained in NYDA^® with low viscosity is potentially flammable, similar to hairspray or perfume. However, dimethicones only ignite when they come into contact with an external ignition source (e.g., open flame). The flammability of different dimethicones varies.
Since the launch of NYDA^® in 2006, no incidents related to the flammability of NYDA^® have been reported. Today, NYDA^® is the most purchased head lice product on the German market, whose reliability and safety is proven. 
To prevent possible accidents, the flammability of NYDA^® as well as the correct handling of the product on the package and in the instructions for use are described as follows: "Because some ingredients are flammable, NYDA^® may not be used in the presence of an open flame or incandescent objects! Keep NYDA^® away from heat and ignition sources and do not smoke during treatment."

This procedure is related to the life cycle of the head lice. Since head lice are very resistant, there is the possibility that some of them were not yet destroyed during the first treatment. The larvae hatch from their eggs after 7 to 8 days. Therefore, it is necessary to check the hair again after 8 to 10 days. A further treatment after 8 to 10 days can kill the young lice that have hatched from the remaining eggs in the meantime. This second treatment is intended to break the life cycle (recommended by the Robert Koch Institute).

Because NYDA^® has a physical effect and attacks the insect's breathing system, it is thought to be effective against itch mites and other types of lice. However, there are no research results.

Dimethicone are a group of linear polydimethylsiloxanes, which are normally colourless, odourless and water repellent liquids. Polydimethylsiloxanes have a low surface tension and are therefore capable of wetting most surfaces. This is crucial for the physical action against head lice. 
Dimethicones are toxicologically safe. They are neither absorbed by the skin, nor by the mucous membrane. In medicines and cosmetics, they are used as ingredients for skin protection ointments, hair styling products, perfume and toothpaste.

Traditional insecticides contain substances with a neurotoxic active principle, i.e., they damage the nervous system of head lice. NYDA^® has a physical mode of action and, unlike other pediculicide, contains no toxins. 
A major weakness of neurotoxic preparations is their mode of action. The nervous system of unhatched head lice is developed after only 4 days. This means that neurotoxic products in most cases have almost no effect on eggs at this stage. Resistance to neurotoxic drugs has also been demonstrated in several countries.
In contrast to NYDA^®, neurotoxic preparations are often not well tolerated. An improper application with regard to the dosage and the application time can produce side effects. Children are particularly sensitive to these effects because their immune system as well as their metabolism and the skin's protective layer are not yet fully developed.

At eight hours for NYDA^® and one hour for NYDA^® plus, the application times of the two products differ. They are equally effective: The outstanding effectiveness against lice in all their development stages has been scientifically proven for NYDA^® and NYDA^® plus.

The background is that there is the listing for NYDA^® in the list of disinfestants as well as the eligibility for reimbursement for children up to 12 years of age or for adolescents with developmental disorders up to 18 years of age. Both listings are linked to a clinical trial conducted with NYDA^® with an application time of 8 hours.

Recent scientific knowledge for NYDA^® plus shows that the outstanding effect is already evident after an hour of application. On this basis, the application time for NYDA^® plus was set to one hour.