GB2413074A - Depilatory method - Google Patents

Abstract

In a depilatory method ultrasonic energy is applied to a depilatory composition on the skin, in order to boost its depilatory action. The preferred depilatory is thioglycolic acid.

Description

1 2413074

APPARATUS AND METHOD

This invention relates to depilation - the removal of hair from human skin by means of a composition.

There are known depilatory compositions which can be applied to areas of the skin to facilitate hair removal.

lo These depilatory compositions employ a depilatory agent which, when in contact with body hair for a period of time, causes hairs to detach or weaken by degrading keratin. After the depilatory composition has caused the hair to break down, it is removed from the skin, for example by washing or wiping.

Depilatory compositions must be applied to and left on the skin for sufficient time to cause hairs to detach, or weaken sufficiently. However, it is undesirable to leave them on the skin for longer periods than are necessary to produce the depilatory effect. In fact many users do not have the time or patience to wait for the depilatory composition to achieve a good result.

The present invention aims to improve depilation efficiency so that better hair removal is achieved and/or a shorter contact time may be employed.

According to a first aspect of the present invention there is provided a depilatory method in which method: (i) a depilatory composition is applied to an area of skin to be depilated; (ii) ultrasonic energy is applied to the depilatory composition while the composition is in contact with the skin; and (iii) after application of ultrasonic energy the composition together with entrained hair is removed from the skin.

lo The depilatory composition may be applied by rubbing or spreading onto the skin. The depilatory composition may be applied with the hands. Alternatively, an applicator may be employed.

The composition and depilated hairs may be removed by washing with water, and/or by wiping and/or scraping the composition from the skin.

The depilatory composition contains a depilatory agent, namely a substance capable of degrading keratin.

Suitably, the depilatory agent comprises at least 0.1% by weight of the depilatory composition, preferably at least 0.5%, more preferably at least 1%, and most preferably at least 2%.

Suitably, the depilatory agent comprises up to 15% by weight of the depilatory composition, preferably up to 10%, more preferably up to 6%, and most preferably up to 4%.

In this specification when we specify an amount of "a" or "then component we do not exclude the possibility that there may be more than one such component. When there is more than one such component the amount stated applies to such components in total.

In this specification percentage values given for a component are percentages by weight of the entire composition, unless otherwise stated.

Suitably, the depilatory agent comprises sulphur compounds lo such as potassium thioglycolate, dithioerythritol, thioglycerol, thioglycol, thioxanthine, thiosalicylcic acid, N-acetyl-L-cysteine, lipoic acid, NaHSO3, LiS, Na2S, K2S, MgS, CaS, SrS, BaS, (NH4)2S, sodium dihydrolipoate 6,8-dithiooctanoate, sodium 6,8-dithiooctanoate, salts of hydrogen sulphide for example NaSH or KSH, thioglycolic acid, thioglycerol, 2-mercaptopropionic acid, 3- mercaptopropionic acid, thiomailic acid, ammonium thioglycolate, glyceryl monothioglycolate, monoethanolamine thioglycolate, monoethanolamine thioglycolic acid, diammonium dithiodiglycolate, ammonium thiolactate, monoethanolamine thiolactate, thioglycolamide, homocysteine, cysteine, glutathione, dithiothreitol, dihydrolipoic acid, 1,3-dithiopropanol, thioglycolamide, glycerylmonothioglycolate, thioglycolhydrazide, keratinase, hydrazine sulphate, hydrazine disulphate, triisocyanate, guanidine thioglycolate, calcium thioglycolate and/or cysteamine.

Suitably, the depilatory composition comprises a base. The base may comprise an alkali metal hydroxide, for example potassium hydroxide. Alternatively, or in addition, the base may comprise an alkaline earth metal hydroxide, for example calcium hydroxide.

The depilatory composition may comprise at least 0.1% of a base, preferably at least 0.5%.

The depilatory composition may comprise up to 20% of a base, preferably up to 10%, and most preferably up to 5%.

Suitably, the depilatory agent is regarded as effective when the pH of the composition is above a threshold value, lo (which we regard as 11.5 but which in different compositions could be regarded as lo, or 10.5, or 11, or 12) and ineffective at pH values below the threshold value.

Suitably, the composition comprises sufficient base to adjust the pH to a value above the threshold value.

References to pH values given herein refer to pH at ambient temperature and pressure.

Suitably, the depilatory composition comprises urea.

Suitably the depilatory composition may comprise at least 0.1% urea, preferably at least 0.5%.

Suitably the depilatory composition may comprise up to 20% of urea, preferably up to 10%.

Suitably, the depilatory composition further comprises a diluent. Suitably, the diluent comprises water.

Suitably, the diluent forms the balance of the depilatory composition. Suitably the composition comprises at least 60\ of a diluent. Suitably the composition comprises up to 90% of a diluent, preferably up to 80%.

Suitably, the depilatory composition comprises further components in an amount of from 5 to 30% by weight, preferably from 10 to 20% by weight.

The depilatory composition may have a viscosity of at least 100 centipoise, for example at least 1,000 lo centipoise, and preferably at least 10,000 centipoise.

The composition may have a viscosity of less than 1,000,000 centipoise, preferably less than 500,000 centipoise, more preferably less than 200,000 centipoise.

Suitably, for this definition the viscosity is measured with a commercially available Brookfield DV II viscometer using spindle LV3 at a temperature of 22 C.

Preferably, the ultrasonic energy is supplied by an ultrasonic device which is portable. A suitable ultrasonic device may be a hand held ultrasonic transmitter. Preferably, the ultrasonic device comprises a transmitter and power source in a single unit which may be held by a user in one hand.

Preferably, the ultrasonic device is of the type having a battery and ultrasonic generator in a main body part which is grasped by a user, and which has a tapering part leading to a contact head, of chisel-like shape. Suitably the head is at least 0.5 cm long, preferably at least 1 cm long. Suitably the head is up to 5 cm long, preferably up to 3 cm long. Suitably the head is at least 0.2 mm wide, preferably at least 1 mm wide. Suitably the head is up to 4 mm wide, preferably up to 3 mm wide. A device of this type is commercially available from Kao Corporation, Japan.

Suitably, the ultrasonic device emits ultrasound waves having a frequency of at least lOkHz, preferably at least 20kHz. The ultrasonic energy suitably has a frequency of up to lOMHz, preferably up to 5MHz, more preferably up to lMHz, yet more preferably up to 150kHz, and most preferably up to 100 kHz. Preferably, the ultrasonic lo device emits waves having a frequency of between 30 and 80 kHz, for example around 50kHz.

The ultrasonic waves are desirably of such a frequency that they provide a beneficial depilatory effect in combination with the depilatory composition. The ultrasonic waves are desirably of such a frequency that when the ultrasonic device is employed according to the method of the invention substantially no damage is caused to the skin.

Suitably, ultrasonic energy is applied to an area of the body to be depilated from an ultrasonic device having a transmitting head which is arranged not to make contact with the body. Suitably, the ultrasonic device comprises spacing means, which may comprise a collar, arranged to keep the transmitting head in spaced relationship from the body. Suitably, the spacing means is arranged to contact the skin such that the transmitting head of the ultrasonic device is maintained a short distance from the skin.

Suitably, said short distance comprises between 0.1 and lOmm.

Preferably the transmitting head of the ultrasonic device is in contact with the depilatory composition, such that ultrasound waves do not travel through air before reaching the depilatory composition.

The method of the invention may be of a nature as to be safely performed by an untrained operator, for example by a person in their home. Alternatively, or additionally, the method according to the present invention may be lo performed by a professional beautician.

Preferably, the depilatory composition is left on the skin for 1 minute, more preferably at least 2 minutes, and most preferably at least 3 minutes. Preferably it is left on the skin for up to 10 minutes, more preferably for up to 8 minutes, and most preferably for up to 5 minutes.

The depilatory composition may be applied to and left on an area of the skin for a time preceding the application of ultrasonic energy thereto. In such a case the depilatory composition is suitably left on an area of the skin prior to the application of ultrasound for up to 8 minutes, preferably for up to 4 minutes, and most preferably for up to 2 minutes. In such a case, the depilatory composition is left on an area of the skin for at least 30 seconds prior to the application of ultrasound thereto, more preferably for at least 1 minute.

The depilatory composition may be left on an area of the skin for a time following the end of the application of ultrasonic energy thereto. In such a case, the depilatory composition is suitably left on an area of the skin after the end of the application of ultrasonic energy thereto for up to 8 minutes, preferably for up to 4 minutes, and most preferably up to 2 minutes. In such a case, the depilatory composition is suitably left on an area of the skin for at least 30 seconds following the end of the application of ultrasound thereto, more preferably for at least 1 minute.

Suitably, after the end of the application of ultrasonic energy to depilatory composition on the area of the skin and preferably after the depilatory composition has then been left to stand for a time, the depilatory composition is removed.

Preferably, according to the method, ultrasonic energy is applied to depilatory composition on a given area of the skin for at least 5 seconds, more preferably for at least seconds, more preferably for at least 30 seconds, for example at least 45 seconds. Preferably, according to the method, ultrasonic energy is applied to depilatory composition applied on a given area of the skin for up to 8 minutes, more preferably up to 4 minutes, more preferably up to 2 minutes, for example up to 75 seconds.

Suitably, according to the method ultrasonic energy may be applied for up to 10 minutes but the device may be moved over the skin such that at any given time depilatory composition applied to an area of the skin has ultrasonic energy applied thereto while depilatory composition applied to one or more other areas of the skin does not.

Preferably ultrasonic energy is applied to the skin only when the depilatory composition is present thereon According to the method the ultrasonic device may be moved over the skin in "passes" such that ultrasonic energy is applied to depilatory composition applied to a first area of the skin for a time then the ultrasonic energy is applied to depilatory composition applied to another area for a time and then it is applied once more to the first area. For example, the ultrasonic device could be moved up and down over a user's leg having depilatory composition applied thereto.

It is believed that the application of ultrasonic energy may cause cavitation within the depilatory composition which may increase the rate of hair breakdown. However the present invention is in no way limited by this provisional explanation.

Suitably, according to the method, the application of ultrasonic energy may cause an increase in the temperature of the depilatory composition. Suitably, according to the method, the temperature of the composition may be caused to increase by between 1 and 15 C following application of the composition to body. Suitably, the temperature increases by between 2 and 10 C, for example by around 5 C. Suitably, the temperature of the composition does not exceed 40 C whilst in contact with the body. This effect may be greatest during the third stage of the depilation process.

Suitably the ultrasonic device comprises spacing means, which may comprise spacing means arranged to hold the transmitting head in spaced relationship relative to a user's body during employment in a depilatory method.

Suitably, the spacing means comprises a collar. Suitably, the collar comprises an open ended tube encircling the transmitting head of the device.

Suitably, the spacing means is arranged to contact the skin such that the transmitting head of the ultrasonic device is maintained a short distance from the skin.

Suitably, said short distance comprises between 0.1 and lOmm.

According to a second aspect of the present invention there is provided a depilatory kit comprising: (a) a depilatory composition comprising a depilatory agent; and (b) an ultrasonic device having an ultrasonic transmitting head.

Suitably, the depilatory composition is as described in respect of the first aspect.

Suitably, the ultrasonic device is as described in respect of the first aspect.

Suitably, the depilatory kit further comprises instructions for the carrying out of a depilatory method according to the first aspect employing the depilatory composition and ultrasonic device in combination.

Specific embodiments of the present invention will now be described by way of example with reference to the accompanying drawing in which Figure 1 is a schematic view of an efficacy tester apparatus.

Example 1

A depilatory composition was prepared having the following formulation: 3.0% by weight of thioglycolic acid lo potassium hydroxide sufficient to adjust pH to 12.5 deionized water (balance) The change in the depilatory action of the composition when employed with and without ultrasound was then determined according to the following efficacy test method.

The method employed a commercially available tensile testing machine. This was set up to record the force required to cause a given strain on a hair and to measure how that force changes over a period of time.

When a depilatory agent acts on hair it causes it to weaken such that over time a progressively weaker force is required to keep the hair stretched by a given amount.

After a certain period of time the hair becomes so weak it requires practically no force to stretch or break the hair.

As illustrated by Figure 1 the testing arrangement comprised a clamp 1, forming part of the tensile testing machine, for clamping the ends of a hair 3.

The testing arrangement further comprised a hook 2 for applying a force to the middle of the hair 3 to hold the hair 3 taut and a bath 4 for containing the depilating composition 5 into which the section of the hair 3 held by hook 2 was immersed.

The efficacy test employed six long, pristine, kink-free hairs. Each hair was cut in half to give a root half and a tip half. Each hair then produced either a root half or 0 a tip half tested with the use of ultrasonic energy and the other half was tested without the use of ultrasonic energy. This was alternated between tests.

For the tests without ultrasonic energy the hair 3 was set up on the tensile testing machine by hooking the bottom and securing the ends in the clamp 1 such that the hair 3 was held under a 20g force. Once the reading of force was stable (+/- 0.2g over 1 minute) 12 ml of depilatory composition 5 was poured into the bath 4 in which the hooked section of the hair 3 was held such that the bottom loop 3a of the hair 3 was just submerged.

The drop in the force required to maintain the strain was then measured over time until the required force reached zero.

For the test with ultrasound the method above was repeated with the additional step that before pouring depilatory composition 5 into the bath a hand held ultrasonic device 6 mounted in place to have its transmitting head 7 immersed about lam in the depilatory composition 5, and about lam from the bottom loop 3a of the hair. The device was switched on and left on until the required force reached zero.

The efficacy of the depilatory method employing ultrasound was then determined in comparison with the non-ultrasonic method.

The results are set out in the table below. The time (T) stated was the time taken for the required force to reach lo zero.

Without Ultrasonics With Ultracnica TEST Time (T) Time T(U) Ratio (seconds) (seconds) (T(U)/T) 1 643.3 347.4 0.54 (root half) (tip half) 892.1 422 0.47 (tip half) (root half) 3 807.2 538.9 0.67 (root half) (tip half) 4 807.2 516.1 0.64 (tip half) (root half) 1046 516 0.54 (root half) (tip half) 807.8 554.5 0.69 (tip half) (root half) AVERAGE I 834 490 0.59 Standard 132 86 deviation The results set out above clearly indicates that the depilatory action of the depilatory composition was greatly enhanced by the use of ultrasonic energy.

Statistical analysis showed the improvements to be statistically significant (p-value = 0.0003).

Claims (11)

1. A depilatory method in which method: (i) a depilatory composition is applied to an area of skin to be depilated; (ii) ultrasonic energy is applied to the depilatory composition while the composition is in contact with the skin; and (iii) after application of ultrasonic energy the composition together with entrained hair is removed from the skin.

2. A method as claimed in claim 1 wherein the ultrasonic device emits ultrasound waves having a frequency of at least 10 kHz.

3. A method as claimed in claim 1 or 2 the ultrasonic device emits ultrasound waves having a frequency of up to MHz.

4. A method as claimed in claims 2 and 3 wherein the ultrasonic device emits ultrasound waves having a frequency of 20-100 kHz.

5. A method as claimed in any preceding claim wherein the ultrasonic energy is applied to depilatory composition on a given area of the skin for at least 5 seconds.

6. A method as claimed in any preceding claim wherein the ultrasonic energy is applied to depilatory composition on a given area of the skin for up to 8 minutes.

7. A method as claimed in any preceding claim wherein the source of ultrasonic energy has ultrasound emitting means which is in contact with the depilatory composition.

8. A method as claimed in any preceding claim wherein the lo depilatory composition has the following characteristics: it has 0.1-15% w/w of a sulphur-containing depilatory agent; 0.1-20% w/w of a base; and 60-90% w/w of a diluent - it has a pH of at least 11.5 - it has a viscosity in the range 100-200,000

centipoise (measured on a Brookfield DVII

viscometer, spindle LV3, at 22 C).

9. A method as claimed in any preceding claim wherein the temperature of the composition on the skin rises by between 1 and 15 C during the application of ultrasonic energy.

10. A depilatory kit comprising: (a) a depilatory composition comprising a depilatory agent; and (b) an ultrasonic device having an ultrasonic transmitting head.

11. A depilatory method or kit substantially as hereinbefore described with particular reference to the accompanying examples and drawings.