Phthirus pubis infestations commonly known as “crabs” are found worldwide. Pubic lice usually are spread through sexual contact but occasionally may be spread by close personal contact or contact with articles such as clothing, bed linens, and towels that have been used by an infected person.1,2
Typically, pubic lice cause itching in the area covered by pubic hair, which can develop into erythematous sore lesions due to scratching of bites.
Similar to head lice, these egg-laying blood-sucking lice are effectively treated with permethrin and deep cleaning of all materials to eliminate any egg stores. When pubic lice are unable to find a suitable place to lay eggs, it ends their lifecycle.3
The incidence of pubic lice infestations is estimated to be between 1.3% and 4.6%, with an average incidence of 2% worldwide.4,5
It is estimated that 70% to 80% of adults now remove pubic hair in part or entirety.5–7 There are various methods and degrees of hair removal available, thought to offer comfort and cleanliness to its users.
There is also some evidence to suggest that the destruction of this pubic hair habitat may account for the falling incidence of pubic lice and may possibly lead to its eradication or atypical presentation.8–10
To report the changing incidence of pubic lice infestation from our unit over the last 10 years and assess its association if any with pubic hair removal of any kind.
Medical records of patients with confirmed pubic lice infestation were reviewed from our unit. All data were anonymized and local ethics approval was granted. The date range August 2003 to August 2013 was selected. Five hundred randomly allocated anonymous questionnaires were sent out to all clinic visitors regardless of diagnosis, from each year to ascertain whether they had any pubic hair removal. In total, 5000 questionnaires over the 10-year period were sent out. Four questions were asked:
How much is removed?
- Do you or did you ever remove any of your pubic hair?
What was the reason for this?
- 1. Total 2. Partial 3. None but trimmed 4. None
What method of hair removal do you use – you can select more than one?
- 1. Cosmesis 2. Hygiene 3. Religious reasons 4. Other
- 1. Shaving 2. Trimming 3. Waxing 4. Laser 5. Chemical Cream/Gel 6. Other
IBM SPSS Statistics 22.0 was used for statistical analysis to compare the changing incidence of pubic lice infestation and hair removal using Pearson rank correlation coefficient and appropriate χ2 tests.
For demographic data, refer to Tables 1 and 2.
Seventy-seven percent (3850) of our patients returned questionnaire of the 5000 initially sent out.
When reviewing the incidence rates over the 10-year period, we found that the incidence of pubic lice has continually fallen from 1.82% to 0.07% (Fig. 1). When comparing the incidence of infection between 2003 and 2013, using the χ2 test for association with Yates correction, we found a P value less than 0.001, suggesting a strongly significant decrease in incidence.
Among patients who had confirmed pubic lice infections, when reviewing their records, we found that 94.21% of these patients had documented records suggesting no pubic hair removal.
We also observed that the overall incidence of pubic hair removal has increased from 33.2% to 87.1% over the same 10-year period (Fig. 2). When comparing the hair removal incidence between 2003 and 2013, using the same χ2 test with Yates correction, we found a P value less than 0.001, suggesting, again, a significant increase.
The comparison of these 2 observations is shown in Figure 3, where we can clearly identify a highly significant and strong correlation between the falling incidence of pubic lice infections and increase in pubic hair removal. Pearson correlation gives an r value of 0.9686 (95% confidence intervals, 0.88–0.992) and has a P value less than 0.0001.
Our questionnaire aimed to identify reasons and methods of hair removal. Figure 4 shows that the reasons for hair removal from our population were only identified as follows: hygiene and cosmesis. The Pearson correlation coefficient r values were 0.9719 (95% confidence intervals, 0.953–0.992) for cosmesis and 0.9781 (95% confidence intervals, 0.932–0.9813) for hygiene, both of these correlations have been shown to be significant, with P value less than 0.001.
Our population suggests that shaving remains the most common method of hair removal (mean, 70.36%). Waxing and laser hair removal have become increasingly popular, whereas trimming and chemical methods are less popular, as seen in Figure 6.
The pattern of hair removal has also changed during our observed period. In 2003, 56.38% of patients had no hair removal, which dropped to 12.45% in 2013. The incidence of both total hair removal and partial hair removal has increased from 19.21% to 31.23% and from 23.57% to 56.32%, respectively (Fig. 6).
The Pearson correlation coefficients were used to identify the strength of linear relationships when charting the amount of hair removal. Total hair removal has a Pearson correlation coefficient r value of 0.966 (95% confidence intervals, 0.913–0.972), with a P value less than 0.0001. Partial hair removal has a Pearson correlation coefficient r value of 0.918 (95% confidence intervals, 0.892–0.926), with a P value of 0.001. No hair removal has a Pearson correlation coefficient r value of 0.910 (95% confidence intervals, 0.903–0.928), with a P value less than 0.0001, and finally, trimmed pubic hair has a Pearson correlation coefficient r value of 0.536 (95% confidence, intervals 0.523–0.541), with a P value of 0.721.
Over the examined 10-year period, we have found a clear and significant decrease in the incidence of pubic lice infestation from our unit. Figure 1 shows the incidence falling from 1.82% in 2003 to 0.07% in 2013 (P < 0.001). During that same period, Figure 2 highlights a significant increase in the incidence of pubic hair removal, increasing from 33.2% in 2003 to 87.1% in 2013 (P < 0.001).
Figure 3 demonstrates a strongly significant linear correlation between these 2 variables, with a Pearson correlation r value of 0.9686 (95% confidence intervals, 0.88 to 0.992) and a P value less than 0.0001.
These results support the hypothesis that increased incidence in pubic hair removal is associated with the falling incidence of pubic lice infections and expands on the work of previous studies that have drawn similar conclusions that without pubic hair being present, it is difficult to establish infection.9,10
The reasons for pubic hair removal are many; however, within our sample, cosmesis and hygiene were the only 2 reasons identified (see Fig. 4). Cosmesis over the 10-year period has shown a strong positive correlation, having an r value of 0.9719 (95% confidence intervals, 0.953–0.992) and a P value less than 0.001. We can hypothesize that the reason for this may be due to the increased media coverage. The use of magazines, celebrities, and chat shows, promoting openness of pubic hair removal, has made it fashionable. With numerous patterns and styles being advertised, it is clear that it has gained in popularity.7
The mean age of patients within our sample was 24.32 years. We hypothesize that this age group of people is composed of those who are most influenced by what society may regard as “cool” and so are likely to be influenced by these media campaigns regarding pubic hair removal.
This is supported by the increase in both total hair removal (r = 0.966 [95% confidence intervals, 0.913–0.972; P < 0.0001) and partial hair removal (r = 0.918 [95% confidence intervals, 0.892–0.926; P = 0.001) over this period (see Fig. 5).
The incidence of no hair removal has also shown a strong negative linear correlation over the same period, with an r value of 0.910 (95% confidence intervals, 0.903–0.928; P < 0.0001), suggesting that it is significantly less popular.
Throughout all the years, our data suggest that pubic hair removal remains more common in women than in men, although the proportion of men undertaking some sort of hair removal is increasing. We also noted that although overall pubic lice infections reduced, there was a shift from it being relatively evenly distributed between the sexes to it becoming more prevalent in men (see Table 2). This may be due to the reduced amount of hair removal proportionally when compared with women, again supporting the hypotheses and previous work.9,10
Figure 6 shows the several methods of hair removal identified from our study population. The most popular of these remains shaving, with a mean 70.36% of patients using this method. Despite the increasing incidence of waxing and laser use, we believe that the popularity of shaving is due to the cost-effectiveness offered by this method. Specific cost analysis was out of the scope of this study, but it is an important factor that may influence the method chosen to remove pubic hair.
The limitations of our study are that we have used correlations to show associations and so are limited because these do not prove that casual relationships exist between our variables. However, the correlations are very strong and have narrow confidence intervals, and so we feel that there may be a significant relationship between hair removal and incidence of lice infection if further studies were done.
The second limitation is that of recall bias regarding hair removal, as we were reliant on the answers provided by our questionnaires, which may not be truly representative. This must also be considered in the context of a wider population, as our sample was mainly a young white group, and so our conclusions may not hold true in areas where this is not the case.
The exact causal relationship would be better demonstrated using a case-control study. However, this study logistically provides more challenges because it, too, is also prone to recall bias and can have difficulty in establishing a temporal relationship between exposure and outcome.
Pubic lice infestations are in decline, and there is a growing body of evidence that it is associated with the increased incidence in removal of pubic hair. As culture and practice changes, we may see a changing atypical pattern of pubic lice infestations, as they try to colonize other habitats such as chest or eyebrow hair. We may even see its complete eradication and no longer have patients presenting with pubic lice, within the sexual health setting.
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