results in an eczematous reaction at the site of application (Figure 7.5).
Table 7.1 Uses of Wood’s light in vulval disease.
| Disease | Fluorescence colour |
|---|---|
| Vitiligo | Bright white |
| Infections | |
| Pseudomonas | Green |
| Erythrasma | Coral‐red |
| Tinea capitis – Microsporum species | Bright green |
| Tinea capitis – Trichophyton schoenleinii (Note: Other trichophyton species do not fluoresce) | Blue |
| Pityriasis versicolor | Copper‐orange |
Figure 7.3 Allergens for testing placed in plastic trays.
There are standard series that are used in all patients undergoing patch testing, but it is important to extend these for investigation of an anogenital dermatosis. Patients should be referred to a contact dermatitis clinic so that multiple series to include preservatives, fragrances, medicaments, and topical steroids are tested, otherwise relevant allergens may be missed. It is also helpful to test the patient’s own products that have been used, but these may require dilution to avoid severe irritant reactions. Education on sources of any relevant positive allergens is then provided so that they can be avoided in future.
Resources
Recommended patch testing series and patient information leaflets
Figure 7.4 Allergens applied to the patient’s back.
Figure 7.5 Positive reaction showing eczematous reaction at the site of application.
https://cutaneousallergy.org/resources/recommended‐series/
Patient information about patch testing
https://www.bad.org.uk/shared/get‐file.ashx?id=113&itemtype=document. Last accessed September 2021.
https://dermnetnz.org/topics/patch‐tests/. Last accessed September 2021.
Prick testing
If a Type 1 allergic reaction is suspected, this is most likely to be due to either semen or latex in the context of vulval symptoms. Prick testing may be required if this type of allergy is suspected, and the patient should be referred to an allergy clinic, where full facilities for resuscitation are available. It detects allergen specific IgE bound to mast cells which degranulate and release histamine, causing a weal at the site of testing. Oral antihistamines should be stopped a few days beforehand.
A small drop of the allergen is placed on the skin, most commonly on the forearm, and then a small prick is made through the liquid with a lancet. A positive control of histamine is used with a negative control of saline. The tests are read after 15–20 minutes, and an urticarial weal of 3 mm or more is regarded as positive.
Patient information about prick testing
https://dermnetnz.org/topics/skin‐prick‐testing/. Last accessed September 2021.
Blood tests
Routine blood tests are of little value in the investigation of vulval disease. They are mainly used in specific situations.
1 Infection Serological tests are useful in some infections but are targeted towards the suspected clinical diagnosis.
2 Immunobullous disease Indirect immunofluorescence is performed on serum and has two stages. First, an unlabelled antibody binds to the target antigen, and in the second stage a fluorescent antibody against the first antibody is used in detection. In immunobullous disease, however, they are generally confirmatory rather than diagnostic. It is used in conjunction with direct immunofluorescent studies.
3 Type 1 allergic reactions A RAST (radioallergosorbent test) is safer than in vivo prick testing if the patient gives a history of anaphylactic reactions. This measures any interaction between the antigen and its specific antibody. The possible allergen needs to be considered and that specific test requested, as it is not a universal test to determine allergy but rather confirms what is suspected.
Imaging
Radiological imaging techniques are rarely needed for the investigation of vulval dermatoses, but are vital in the management of malignant disease and are helpful in other specific situations [13,14]. The main indications for imaging are shown in Table 7.2, and the most appropriate imaging technique should be discussed with a radiologist.
Ultrasound scanning is not widely used in the investigation of vulval lesions as it can be difficult to identify structures. Magnetic resonance imaging scanning (MRI) gives great detail of both the vulva and vagina. The main use of imaging is in the management of malignant disease, where it can be used to delineate the extent of tumours for treatment planning, prognosis, and monitoring for recurrence and response post treatment. Often, a combination of computerised tomography, MRI and positron emission tomography (PET‐CT) is used [15].
Research studies using MRI scanning and Doppler ultrasound had provided a greater understanding of anatomy and function of structures, especially the clitoris [16,17]. Functional MRI of the brain has also been used to study cerebral sexual excitability and its effect on sexual function [18].
Dermoscopy
Dermoscopy is a dermatological technique used mainly in the diagnosis of pigmented lesions. It is not so easy to use on the vulva as special attachments are required in addition to the hand‐held device. This may give additional
