I live in Indonesia where there are many mosquitoes and products sold for their control.

One such product is this one: enter image description here

The product contains 22ml of liquid, the contents of which likely vary slightly by jursidiction


  • Prallethrin - 1.316% (Wikipedia indicates 1.6% in typical products in India https://en.wikipedia.org/wiki/Prallethrin)
  • Petroleum Distillate (carrier) - Enables the delivery of a product to a surface.
  • Butylated hydroxytoluene (BHT) - preservative
  • Fragrances

They sell a liquid for use in a sprayer like this:

enter image description here

Unlike the plug-in which releases very small amounts of insecticide continuously, a sprayer would be sprayed manually perhaps once or twice a day. The product is sold in quantities of around 300-700ml.

Active ingredients vary by jurisdiction: in the Philippines


  • Water
  • Transfluthrin / Cyfluthrin
  • Isopropanol "wetting agent" - Helps a formula spread across a surface.
  • Benzyl Alcohol - anti microbial preservative
  • Sodium Lauryl Sulfate - detergent
  • Acetyl Tributyl Citrate - Helps ensure even distribution of a product's ingredients.

The Indonesian version is:


  • Water
  • Cybermethrin, imiprothrin, prallethrin
  • Propylene Glycol Butyl Ether and PEG-60 Hydrogenated Castor Oil instead of the Acetyl Tributyl Citrate
  • Methylisothiazolinone & Benzisothiazolinone instead of the benzyl alcohol
  • Ethoxylated Alcohol in place of the SLS

Another company sells a similar liquid product to the Baygon liquid

enter image description here

This is sold in two formulations, the regular and the water-based which notes

enter image description here

'tanpa minyak tanah' (literally 'without ground oil', i.e. paraffin - this is not a very technical term and obviously means that the alternative product contains some kind of petroleum distillate)

Both regular and water-based formulations contain the same active ingredients: 1.14% prallethrin, 0.29% cyfluthrin.

I presume that there are particular properties of prallethrin that make it better for vaporization with an electric plug-in device (which I guess is not close to boiling - this should be evaporation) than certain other pyrethroids, but the question is:

  • if one were to refill the plug-in device with the 'spray'-type 1.14% prallethrin, 0.29% cyfluthrin petroleum-based product, would it be reasonable to expect it to have similar dispersal effectiveness to the 1.32% prallethrin petroleum-based 'vaporizer' product
  • given the existence of 'water-based' and 'petroleum-based' products with the same insecticides, is the 'water-based' less effective at dispersal, and does it have any advantage beyond presumably some sort of antipathy towards hydrocarbon vapours for health reasons.
  • $\begingroup$ In my opinion the only reason for using petroleum based products is that once deposited on plants, they won't be washed away by he next rain. The dispersal effectiveness is a secondary factor. $\endgroup$ – Maurice Oct 19 '20 at 8:43
  • $\begingroup$ these products are anti-mosquito for use inside a home; they are not products for use on crops, so there wouldn't be getting any rain on them. $\endgroup$ – thelawnet Oct 19 '20 at 8:53

In short: the petroleum most likely is used as a solvent.

Small detour: tablets of asperin contain acetylsalicylic acid as the intended active compound. But the tablets contain other chemical compounds as well, for example to retain the active ingredient in «good shape» (e.g., stabilizers, antioxidants, etc.) and not at last, fillers. Because, to moderate the wanted action of aspirin in the body, you possibly need a smaller mass of the pure compound, than your balance at home allows you to measure. Thus, the active ingredient is diluted; you equally could say, it is dissolved in the solid matrix of the tablet.

Now to the pyrethroids in question. Similar to perfume, only a relatively small number of the molecules per cubic foot / cubic metre of air suffices to trigger the action; here, against the insects without triggering nausea / headache etc. to you. (It is a question of balancing the effects, and the cost producing the materials vs. return of investment for the company, too.) Thus, the pyrethroids are distributed as diluted. Given the structures of two of the compounds you mention (they differ)

enter image description here

(prallethrin, source)

enter image description here

(cyfluthrin source

there are no, e.g. hydroxy-groups which could render the substances well soluble in water (hydrophilic). Instead, they are more likely to dissolve in apolar solvents, such as petroleum is, then called «carrier». In the other recipe, the PEG and propylene glycol butyl ether may function as the slowly evaporating solvent (mixture).

(Possibly, the list of ingredients was rearranged for this question; often, the containers list them in decreasing relative amount to the total content.) The list of ingredients from the Philippines still may indicate lots of water in the bottle because simultaneously there are other compounds which may mediate between the polar water and the less polar pyrethroids to yield a solution; especially isopropanol (an organic solvent miscible with water), and the detergent, sodium lauryl sulfate may increase the solubility here.

It may be, that overall the recipe using both prallethrin and a little of cyfluthrin is more efficient or / and is less costly to produce than using the other recipe of prallethrin alone. It may be local legislation setting an upper threshold for one, or the other compound differently in one country, to the other; which may be to protect you directly as a consumer, or the environment in general (they don't decompose well in normal wastewater treatments and thus may enter the food chain). Because the evaporation of an aqueous solution may well differ from one based on petroleum, it is not evident that one may be used to refill the other in the electric nebulizer.

  • $\begingroup$ Hi, to clarify I don't think the ingredients are any particular order - the pyrethroids tend to be about 1-2% of the volume of any such product, but I'm sure that the 'water-based' products from both Indonesia and the Philippines are mostly water. I'm not sure if the electric vaporiser product also contains water, it's possible they wouldn't indicate it in the list of ingredients (which are 'what's inside', not a 'full list of ingredients'). Presumably it would ignite easily if the solvent is a petroleum fraction? $\endgroup$ – thelawnet Oct 19 '20 at 16:48
  • $\begingroup$ While it does seem reasonable that the water-based product might not work well in a device designed to create vapour from a petroleum-based solution, I don't think you mentioned whether it is reasonable to suppose there might be significant differences between a product designed to be 'sprayed', containing pyrethroids dissolved in petroleum, and a product designed to be evaporated, also containing pyrethroids dissolved in petroleum? In both cases presumably it's desirable for the spray to disperse effectively in air? $\endgroup$ – thelawnet Oct 19 '20 at 16:53
  • $\begingroup$ Just because «A» contains much of water (plus the detergent and alcohol) doesn't make it better or worse than petroleum-based formulation «B». While ignition of the petroleum of course depends on the amount of energy delivered, there is an interest to use a fraction of petroleum which does not evaporate not too quickly (not as quick as, say acetone); otherwise, the consumers are occupied with refilling the devices too often to see a benefit in the installation of the devices. And yes, the finer air-dispersed, the more effective (actually both against insects and you [lungs, skin, eyes], too). $\endgroup$ – Buttonwood Oct 22 '20 at 20:49

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