INSECT REPELLANTS

INSECTICIDES

English Abstract

ABSTRACT OF THE DISCLOSURE
The invention relates to insect repellant compositions
of N,N-diethyl-m-toluamide (DEET') in alcoholic solution
and containing PEG 400. The insect repellant compositions
of the invention are found to provide unexpected prolonged
activity over that obtained in corresponding compositions
without PEG 400.

Claims

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WHAT IS CLAIMED IS:
1. An insect repellant which consists essentially of N,N-
diethyl-m-toluamide (DEET) in alcoholic solution, and polyethylene
glycol 400 (PEG 400).
2. An inert repellant of Claim 1 containing 5-50%,
of DEET.
3. An insect repellant of Claim 2 containing 10-40%
of DEET.
4. An insect repellant of Claim 2 containing 15-25%
of DEET.
5. An insect repellant of Claim 1 containing 5-35%
of PEG 400.
6. An insect repellant of Claim 5 containing 15-25% of
PEG 400.
7. An insect repellant of Claim 1, containing other repellants.
8. An insect repellant of Claim 1 containing perfume
oils and/or aroma substances.

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9. An insect repellant according to Claim 1 containing
water.
10. An insect repellant of Claim 1 consisting essentially
of 50 parts by weight DEET, 35 parts by weight PEG 400 and
15 parts by weight isopropanol.
11. An insect repellant of Claim 1 consisting essentially
of 20 parts by weight DEET, 20 parts by weight PEG 400 and
60 parts by weight isopropanol.
12. An insect repellant of Claim 1 consisting essentially
of 12 parts by weight DEET, 8 parts by weight PEG 400, 60 parts
by weight ethanol and 20 parts by weight water.
13. An insect repellant of Claim 1 consisting essentially
of 15 parts by weight DEET, 20 parts by weight PEG 400, 5 parts by weight
water, 2 parts by weight isopropyl myristrate, 57 parts by
weight isopropanol and 1 part by weight lavender oil.
14. An insect repellant of Claim 1 consisting essentially
of 15 parts by weight DEET, 15 parts by weight PEG 400, 5 parts
by weight ethylhexanediol, 57 parts by weight isopropanol, 5
parts by weight water, 2 parts by weight propylene glycol and
1 part by weight perfume oil.

Description

The present invention relates to insec-t repel-
lants, for use on human skin, which ~re based on N,N-
diethyl-m-toluamide (DEET) and have a prolonged activity.
DEET is a known and proven insect repellant
and is generally accepted as a very good "all-round
repellant" [Kochhar, R~Ko ~ Dixit, R.S., Somaya, C.J.;
Indian J. Med. Res., 629 1 January 1974].
For a desirable activity of 6 to 8 hours on
human s~in, a concentra-tion of 30% to 50% is required in
form~lations which are usually customary (ethanolic or
isopropanolic solutions) [Now~k, G.A.; Die kosmetischen
Pr~parate (Cosmetic products). Verlag f~r chem. Industrie
H. Ziolkowsky KG 584 Augsburg 197,53.
The duration of the activity of repellan-t formu-
lations against mosquitoes is usually -tested in vivo on
the yellow fever mosquito (Aedes aegypti) [Lust, S.;
Parf. uO KosmO, 417304 (1960)~o In this test, in
each case 500 female mosquitoes are introduced înto a
35 x 35 x 35 cm cage covered with gauze. The readi-
ness of the mosquitoes to bite is tested by introducing
an arm of the particu ar test person. m e landing,
biting and sucking of a relatively large number of mos-
~uitoes is regarded as the cri-terion of positive readi-
ness to bite.
The repellants are tested in a laboratory at a
temperature of. 22C and at a relative atmospheric humi-
dity of 70 ~ 10%. The test substances are applied
immediately before the start of the experiment. The
amount of 0.1 + 0.01 ml of repellant substance is applied
with a glass rod, as far as possible uni~ormly, to an
area of 100 cm on the lower ~rm of the subject,
Adhesive is -then applied around the edges of -the treated
area. The remaining area of arm is covered with a
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plastic glove, which reaches up to the shouldersO
An influencing of the mosquitoes by secretions from the
skin wh;ch attract the mosquitoes can thereby be
excluded~
The arm treated in this manner is introduced into
the mosquito cage, contact between the open ar~a of the
arm and the gauze being prevented in order to avoid con-
tamination of the gauze and simultaneous loss of repel-
lant substance from -the area of arm~ The arm is
introduced directly after application and at hourly
intervals. The exposure time is in each case
5 minutes. It is assumed that the action of a sub-
stance has ended when at least 2 mosquitoes have sucked
their fill on the treated area during this timespan~
Fig. 1 shows the dependence of the duration of
activity on the DEET concentration, determined by the
method described above. m e concentration of DEET
in % has been plotted along the abscissa and the duration
of activity in hours has been plotted along the ordinate.
The graph shown in Figo 1 shows an un~avourable
pa~h in the area of higher concentrationsO According
to our investigations, this is mostly ~o be attributed
to absorption of the DEETo me absorbed portion o~
DEET is no longer a~ailable for repelling insects7
It is known that other substances, such as per-
fume oils, water, solubilising agents and fats, can be
added to alcoholic solutions of DEET~ These additives
serve to improve the fragrance, consistency, ease of
distribution and~feeling on the skin.
Combinations with other repellant active sub-
- stances [Charlet, E~ Finkel, P., Strickmann, H.; Parf.
u. Kosm. 59, 367 (1978)~ are also known.
Substances have now been sought which reduce the
absorption of DEET by human skin and thus increase the
~5 duration of activity. Surprisingly, it was possible
to find that a significantly reduced absorption and an
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improved duration of activity was achieved by adding
polyethylene glycol 400 (PEG 400). PEG L~O i-tself
has no repellant action.
Figo 2 shows a comparison of ~he duration of
ac~ivity of 20% strength DEET formulations without (1)
an additive and with (2) the addition of 20% of PEG 400 .
The two formula-tions are plotted along the
abscissa, and the duration of activi~J in hours is plot-
ted along the ordinate. I~e duration of the activity
of 20% of DEET in isopropanol is increased from 5.7 hours
to 7.4 hours by adding 20% of PEG 400. m e formu-
lation containing 20% of DEET and added PEG 400 is thus
even superior to a 30/0 strength DEET solution withou-t
an ~dditive in respect of the duration of activity.
A prolonged activity or, at the same activity, a lower
use concentration of DEET has been achieved by the
formulations according to the invention.
The concentration of DEET in the formulations
according to the invention is between 5 and 50%, but
preferably between 10 and 4G%. Concentrations
between 15 and 25% are very particul~rly preferred.
Taking into consideration cosmetic requirements,
the concentration of PEG 400 should be between 5 and ~5/
but preferably between 15 and 25%.
Suitable solvents are monohydric and polyhydric alcohols
such as, for example, Cl-C3-alkanols, such as ethanol,
isopropanol; C2-C5-alkanediols, such as ethylene or propylene
glycol or C3-C6-alkanetriols, such as glycerol Further additives
can be other repeilants [Charlet E Finkel, P.,
Strickmann, H.; Parf. u. KosmO 59, ~7 (1978)]; perfume
oils to cover the intrinsic odour; aroma substances with
their own repellant action (for example lemon oil,
laverlder oil or oil of cinnamon)~ water and cosmetic
bases, such as, ~or example, isopropyl myristate 9
paraffin oil and the like [Schrader, K~y Grundlagen und
Rezepturen der Kosme-tika (Principles and recipes of
cosmetics), Dr. Alfred H~thig Verlag Heidelberg, 1979].

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The formulations according to the invention are
applied, like the known formulations ~lotion/spray) to
freely exposed areas of skin in the correct use amountO
m e preparation and bottling of the lotions and
aerosols according to the invention are effected as
described in Nowak, G.A. [Die Kosmetischen Pr~parate
(Cosmetic products), Verlag f~r chem. Industrie
H. Ziolkowsky KG, 567-588 Aug~burq 1975~.
The examples which follow give a ~ew typical
lO recipes, with parts being parts by weight.
1. DEET 5 parts
PEG 400 5 parts
Isopropanol 90 parts
2. DEET 50 parts
PEG 400 35 parts
Isopropanol 15 parts
3. DEET 20 parts
PEG 400 20 parts
Isopropanol 60 parts
20 4. DEET 12 parts
PEG 400 8 parts
Ethanol 60 parts
Water 20 parts
5. DEET 25 parts
PEG 400 25 parts
- Isopropanol 30 parts
Ethanol 19 parts
Perfume oil 1 part
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/ 6. DEET 15 parts
PEG 400 20 parts
Water 5 parts
Isopropyl myristate 2 parts
Isopropanol .57 parts
Lavender oil 1 part
7. DEET 18 parts
PEG 400 12 parts
Dimethyl phthalate 4 parts
Ethanol 65 parts
Perfume oil 1 part
8. DEET 15 parts
PEG 400 15 parts
Ethylhexanediol 5 parts
Isopropanol 57 parts
Water 5 parts
Propylene glycol 2 parts
Perfume oil 1 part
.
9. DEET 10 parts
PEG 400 12 parts
Paraffin oil 2 parts
Isopropanol 75 parts
Perfume oil 1 part
10. DEET 10 parts
PEG 400 15 parts
Propylene glycol 15 parts
Isopropanol 60 parts
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11. DEET 15 parts
PEG 400 13 parts
Glycerol 10 parts
Water 8 parts
Isopropanol 53 parts
Perfume oil 1 part
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