Psyllium may act as a potent inhalant allergen capable of eliciting asthma symptoms. Other procedures in horses require general anesthesia using an inhalant anesthetic. There is negative skin test to common inhalant allergens and normal serum concentrations of IgE. Intentional inhalation may also result in death via asphyxiation (sudden inhalant death). Such products have a long history of use as topical antiseptics and inhalant decongestants. Tobacco smoke is used as a fumigant and inhalant. Substance abusers also sometimes use the gas as an inhalant. A medicated inhalant can also be added to the steam vapor to help reduce coughs. It has been abused as an inhalant, causing a variety of neurotoxic effects. Street children in the Philippines are most likely to be inhalant abusers. It acts as a vasodilator, and is used as an inhalant recreational drug, poppers. A small number of recreational inhalant drugs are pharmaceutical products that are used illicitly. Toluene is used as an intoxicative inhalant in a manner unintended by manufacturers. Statistics on deaths caused by inhalant abuse are difficult to determine. There is an inhalant or incurrent siphon, and an exhalant or excurrent siphon.