Following are the most common active ingredients in insecticides and the types of pests on which they are most effective:

Synergist
These are chemicals that "activate" some insecticides, maikng them more poisonous to insects and thereby enhancing the effectiveness of the active ingredient. MGK 264 and piperonyl butoxide are two commonly used synergists.

HAZARD: Those insecticides that contain piperonyl butoxide should not be used in homes or other situations where any person is using a prescribed medication for a serious illness since this synergist affects the production of liver enzymes.

Pyrethrin (or synthetic pyrethroids)
This is the name used for those synthetic insecticides that duplicate the botanical insecticide pyrethrum, which is derived from Chrysanthemum cinerariaefolium. Pyrethrins are low in mammalian toxicity but quickly knock down insect pests on contact. Pyrethrins are mainly used in flying-insect space sprays, and they decompose rapidly in fluorescent and natural light, leaving no residue.

HAZARD: Asthmatics and persons sensitive to pollen should avoid inhaling pyrethrin since it may cause a reaction.

D-trans-allethrin
One of the types of synthetic pyrethrin, it is used to control flying insects, often in combination with a synergist, and has a quick knockdown effect.

Resmethrin
This pyrethroid material is also used in the control of flying insect pests and is especially useful in controlling hard-to-kill flying insects such as bees and wasps.

Chlorpyrifos
This contact residual insecticide is particularly effective against roaches. It does not kill roaches on immediate contact because it is formulated to have a long residual life.

Propoxur
A contact residual insecticide, it is also effective against crawling insects and provides some rapid knockdown in addition to the long residual life.

Diazinon
Widely used for control of household, turf, ornamental tree, and garden insect pests, only a premium-grade should be used inside the home and only then when specified on the label.

HAZARD: this is one of the more toxic substances available to the homeowner for control of household pests. It must be used with caution and in strict accordance to label instructions.

Malathion
Another of the commonly used insecticides for control of pests in and around the home, malathion has relatively low mammalian toxicity; however, residual life is not as long as some of the other contact residual insecticides. Only premium-grade malathion should be used inside the home.

Silica gel
A nearly non-toxic material, silica abrades the waxy layer on the insect cuticle, causing the insect to dehydrate and die (provided the relative humidity is low enough). High moisture will cause the silica to lump and lose its effectiveness.

HAZARD: Inhalation of the dust may cause severe irritation.

Boric acid
This material is used in some ant and roach baits. It is a slow-acting but persistent poison. Boric acid USP, sold as an eyewash, is safer to use because of the lower concentration. As a roach powder, boric acid should only be lightly dusted into cracks and crevices. it should never be used on exposed surfaces nor in homes with children.

HAZARD: Boric acid is acutely poisonous if ingested, especially by infants and children.

Arsenicals
These materials were once widely used as insecticides, but owing to their high mammalian toxicity they have been phased out of use. However, sodium arsenate is still used in some ant bait traps and is highly effective, but it must be used with great caution.

HAZARD: Aresenicals are highly toxic to all animals and should never be used in homes with pets or children.

Paradichlorobenzene (PDB)
Crystals and nuggets of PDB are used as fumigants to repel or kill fabric pests like clothes moths and carpet beetles. Fabrics put into storage should be washed or dry cleaned and then stored in sealed containers with PDB.

HAZARD: Do not breathe in PDB fumes.

Napthalene
Flakes of this material are used in the same manner as PDB.

N,N-diethyl-meta-toluamide (Deet)
Widely used as an insect repellent for mosquitoes, biting flies, gnats, no-see-ums, chiggers, ticks, and fleas, Deet is generally formulated with ethyl or isopropyl alcohol. Those repellents with the highest percentage of active ingredient(s) (Deet or dimethyl phthalate) will be the most effective.

HAZARD: Deet is a moderately toxic insecticide; it may cause skin rashes.

Dimethyl phthalate
Another commonly used insect repellent, it is especially effective against mosquitoes, fleas, and chiggers. Unlike Deet, it is a relatively non-toxic material.