Note: Descriptions are shown in the official language in which they were submitted.
27~
The present invention relates to insect repel-
lents~ for use on human skin, which are based on N,N-
diethyl-m-toluamide (DEET) and have a prolonged activity.
DEET is a known and proven insect repellent
and is generally accepted as a very good "all-round
repellen-t" [Kochbar, R~Ko ~ Dixit, R.S., Somaya9 C.J. f
Indian J. Med. ResO 9 629 1 January 197~]~
For a desirable activity of 6 to ~ hour~ on
humar. skin, a concentration of ~0% to 50% by wei~ht is re~uired in
formulations which are usually customary ~ethanolic or
isopropanolic solutions~ LNowak, G.A.,oDiekosmetischen
Pr~parate (Cosmetic products), Verlag f~lr chem.
Industrie H. Ziolkowsky KG~ 5~4 Augsburg 1975~.
m e duration of the activity of repellent formu
lations against mosauitoes is usually tested in vivo on
the yellow fever mosquito ~Aedes aegypti) ~hust5 S~ 9
ParfO u Kosm., 41y304 (1960~o In this test~ in
each case 500 female mosquitoes are introduced in-to 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 particular test person. The landing,
biting and sucking of a relatively large number of mos-
quitoes is regarded as the criterion of positive readi-
ness o bite,
The rep~llent formulations are tested in a laboratory at a
temperature of 22C and at a relative atmospheric humi-
dit~ of 70 + 10%. The test substances = formulations as descri~ed
in the examples are applied immediately before the start of the
experiment. The amount of 0.1 - 0.01 ml of Eormulation is a~plied
with a glass rod, as far as possible uniformly~ to an
area of 100 cm on the lower arm o the subjectO
Adhasive is then applied around the edg~s of the treated
areaO The rem~inlng ~rea of arm is covered with a
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plastic glove, which reaches up to -the shoulders.
An influencing of the mosquitoes by secretions from the
skin which attract the mosquitoes can thereby be
excl~ded.
The ar~ treated in this manner is introduced into
the mosquito cage, contact between the open area of the
ar~. and the gauze being prevented in order to avoid con
tamination of the gau~.e and simultan~ous loss of repel-
lant substance from the area of arm. The arm is
introduced directly after application and at hourly
intervals. The exposùre time is in each case
5 minutes. It is ~ssumed that the action of a sub-
stance has ended when at least 2 mosqui~es have sucked
their fill on the treated area durin~ this timespanO
Fig. 1 shows the dependence of the duration of
activity on the DEET concentrations, deter~ined by the
method described aboveO The çoncentration of DEET in ~ by
weighthas been plotted along the abscissa and the duration
of activity in hours has been plotted along the ordinate.
~he graph sho~n in F.ig~ 1 shows ~n unfavour~ble
Path -n the area of higher concen-trations. According
to o~lr investigations, th s is mostly to be attributed
to absorPtion of the DEET. The absorbed portion of
DEET is no longer available for repelling insectsO
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 ~o improve the fragrance, consistency~ ease of
distribution and feeling on the skin~
3C Combinations with other repelle~t active sub-
s-tances [Charlet, E., Finkel, PO 9 Strickmann, H. 9 ParfO
u~ Kosm 59, 367 (1978)~ are also knownO
Substances have now been sought which reduce the
absorption of DÆET by human skin and thus .increase the
dura-ti.en o~ activityO ~urprisingly, it was possihle
to find that a significantly reduced absorption and an
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improved duration of activity was achieved by adding castor oil. Castor oil it-
self has no repellent action.
Fig. 2 shows a comparison of the duration of activity of 20% by weight
strength DEET formulations without ~1) an additive and with (2) the addition of
15% by weight of castor oil.
The two formulations are plotted along the abscissa, and the duration
oE activity in hours is plotted along the ordinate. The duration of the
activity of 20% by weight of DEET in isopropanol is increased from 5.7 hours to
7.9 hours by adding 15% by weight of castor oil. The formulation containing
20% by weight of DEET and added castor oil is thus even superior to a 30% by
weight strength DEET solution without an additive in respect of the duration of
activity. A prolonged activity or, at the same activity, a lower use concentra-
tion of DEET has been achieved by the formulations according to the invention.
The concentration of DEET in the formulations according to the inven-
tion is between 5 and 50% by weight but preferably between 10 ~nd 40% by weight.Concentrations between 15 and 25% by weight are very particularly preferred.
Taking into consideration cosmetic requirements, the concentration oE
castor oil should be between 5 and 35%, but preferably between 10 and 20% by
weight.
Commercially available castor oil DAB VII is used. Suitable solvents
are monohydric and polyhydric alcohols, particularly alkanols, alkanediols and
alkanetriols, such as, for example, ethanol, isopropanol, propylene glycol or
glycerol. Further additives can be: other repellents LCharlet, E., Finkel, P.,
Stickmann, H.; Parf. u. Kosm. 59, 367 ~1978)~; perfume oils to cover the
intrinsic odour; aroma substances with their own repellent action (for example
lcmon oil, lavender oil or oil of cinnamon), water and cosmetic bases, such as,
for example, isopropyl myristate, paraffin oil and the like [Schrader, K.;
Cr~mdlagen und Re~epturen der Kosmetika (Principles and recipes of cosmetics),
/~
2~S~
Dr~ Alfred H~thig Verlag Heidelberg9 1979]~
The formulations according -to the invention are
appl~ed, like the known formulations (lotion/spray) to
freely exposed areas of skin in the correct use amount.
The preparation and bottling of the lotions anl
aerosols according to the invention are effected as
described in Nowak7 GoAo [Die Kosmetischen Praparate
(Cosmetic products~ Verlag f~r chemO Industrie
H. 7iolkowsky KG, 567-58~, Augs~urg 1975~.
The examples which follow give a ~ew t~pical
reCipes. All parts are parts by weightO
1. DEET 5 parts
Castor oll 5 parts
Isopropanol90 parts
15 2. DEET 50 parts
Castor oil35 parts
Isopropano-15 parts
DEET 20 parts
Castor oil15 parts
Isopropanol65 parts
DEET 12 parts
Castor oil 8 parts
Ethanol 70 parts
Water 10 parts
25 5~ DEET 75 parts
Castor oil10 parts
Isopropanol.45 parts
Ethanol 1~ parts
Perfume oil1 part
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-- 5 --
6. DEET 15 parts
Castor oil 20 parts
Isopropyl myristate2 parts
Isopropanol57 paL ts
Water - 5 parts
L avender O i 11 part
7. DEET 18 parts
Castor oil . 12 parts
Dimethyl phthalate4 parts
Ethanol 65 parts
Perfume oil 1 part
8. DEET 15 parts
Castor oil 15 parts
Ethylhexanediol5 parts
Isopropanol 57 par-ts
Water 5 parts
Propylene glycol2 parts
Perfume oil 1 part
9. DEET 10 parts
Castor oil 14 parts
Paraffin oil 3 parts
Isopropanol 72 parts
Perfume oil 1 part
10. DEET 10 parts
Castor oil 10 parts
Propylene glycol20 parts
Isopropanol 59 parts
Perfume oil 1 part
11. DEET 12 part~
Castor oil 15 parts
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-- 6 --
Isoprc,p~l myristate 3 par-ts
Isopropanol 62 parts
Glycerol 8 parts
Preparation of -the lotions:
The lormulations of Examples 1 to 11 are prepared by mixing
the constituents in the indicated order.
Production of aerosols:
The formulations of Examples 1 to 11 can be used as the
solution of active compound for the aerosols. The lotion is
poured into a standard commercial aerosol can and sealed with
the valve.
The propellant is introduced through the valve.
Example using propane/butane as propellant:
lotion according to
Example 8 60 parts
propellant
propane/butane 40 parts
Example using fluorinated hydrocarbons as the propellant:
lot ion according to
Example 2 50 parts
propellant
trichl~rofluoromethane and
dichlorodifluoromethane50 parts
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