History taking: a key element in dermatology
Chronic pruritic dermatitis can pose a diagnostic challenge and its treatment can be even more challenging. In many cases the disease is long-standing and multifactorial, which necessitates elucidation and above all adaptation of the case to the owner's motivations. It is therefore essential to take a clear and detailed history, ideally comprising two distinct phases: the first involves a closed and exhaustive questionnaire, whilst the second phase comprises very open questioning to reiterate certain points raised in the questionnaire but also to determine the motivation and means available to the owner.
1/ Data collection
Numerous elements are needed for the diagnosis and establishment of a therapeutic protocol. To ensure that nothing is overlooked, a questionnaire can be a very useful aid (Table 1, Figure 1). The owner is asked to fill it out, with the help of a nurse if necessary. We then go over the important elements of this questionnaire during the consultation. This approach ensures that nothing is overlooked and we can then concentrate on the most essential elements in the second phase of the visit.
2/ Listen to the owner
By allowing the consultation to take place in a very open manner one can identify two essential elements for the implementation of an effective treatment protocol: the expectations of the owners and any difficulties encountered with previous prescriptions. One of the common problems encountered in practice is the ability of the practitioner to put themselves in the owner’s shoes. By allowing the people who are requesting the treatment to express themselves, it is easier to adapt the treatment to them and their capacities.
Also, open questions often reveal anomalies that can be packed with information, such as erratic food intake, places that the dog visits and the owner forgot to mention on the first questionnaire (workplace, neighbours, car etc.), reactions to topical products, inappropriate applications of topical products, etc.
A recent study revealed that more answers are obtained by open questions (Dysart, 2011). It is therefore important to allow the owners to express themselves without interrupting them. The most useful information is often obtained at the end of the history taking phase, by going back over certain aspects from a different angle.
3/ Diagnostic value of the information obtained
The principal diagnostic aids provided by this step are summarised in Table 2.
There are numerous breed predispositions for pruritic dermatitis (Table 3). In practice, the most useful are those for atopic dermatitis, syringomyelia, demodectic mange, behavioural disorders, and primary Malassezia dermatitis.
B) Age at onset of lesions
Any pruritus that starts in a young animal (under 6 months) should invoke a diagnosis of ectoparasitic disease, or even an allergic dermatitis in some breeds (Westie, French bulldog, Shar Pei); in adults, consider ectoparasitic disease or allergic dermatitis, whilst in elderly dogs certain neoplastic disease should also be envisaged (cutaneous lymphoma, metabolic diseases, endocrinopathies); In animals under one year of age, a dietary cause is more common in cases of atopic dermatitis (Picco, 2008).
C) Circumstances surrounding the onset
Certain circumstances of onset can help to orientate the diagnosis:
• A recent stay in a boarding kennel, recent contact with other animals, indirect contact with foxes: ectoparasites (fleas, sarcoptic mange),
• Recent infestation with fleas: lice, flea allergy dermatitis, atopic dermatitis,
• Use of topical products: contact dermatitis, granular para-keratosis,
• Provoked by stroking or massages around the neck or after pulling on the lead: syringomyelia,
• After a visit to the grooming parlour: contact dermatitis, ectoparasites, ringworm,
• Following flea infestation: flea allergy dermatitis, atopic dermatitis,
• Lifestyle and environment.
The habitat provides vital information for the diagnosis of a possible contact allergy (where the animal sleeps for example), flea infestation, or trombiculiasis.
The lifestyle is very important in that it can be directly responsible for pruritic dermatoses:
• Exposure to the sun (solar dermatitis, actinic keratosis),
• Hierarchical disorders (licking dermatitis, alesional pruritus),
• Frequent baths (suppurative otitis, ineffective flea treatment), direct or indirect contact with wildlife (dermatophytosis), with foxes (sarcoptic mange),
• Hunting (traumatic folliculitis, dermatophytosis, ectoparasitic diseases: trombiculiasis, sarcoptic mange),
• Group housing (ectoparasitic disease: fleas, Sarcoptes, Cheyletiella).
F) Living areas
It is important to be aware of all of the living areas frequented by the animal to implement effective and comprehensive external parasite control, but also to identify zones of parasitic contamination that are often overlooked by the owners.
Knowledge of the animal’s diet enables the implementation of an appropriate exclusion diet or the identification of any dietary imbalances. Recording every meal or titbit that the animal receives may prove difficult; the owners often omit numerous instances of food intake (breakfast, treats, titbits, walks, etc.).
Contrary to common belief, animals fed on red meat do not present a higher risk of developing food allergy than those fed on white meat.
H) Previous disease history
The existence of gastrointestinal disorders associated with the pruritus is indicative of a food allergy. The presence of rhinitis or conjunctivitis may indicate an allergy to airborne allergens. A previous history of urticaria or angioedema is often considered as a minor diagnostic criterion for canine atopic dermatitis.
I) Progression of symptoms over time and seasonality of the pruritus
The existence of regular itching in specific sites is indicative of atopic dermatitis or flea allergy dermatitis. Pruritic dermatitis that arises primarily in the summer or autumn is indicative of parasitic dermatoses (trombiculiasis etc.) or allergies such as flea allergy dermatitis or more rarely pollen allergy.
J) Topography at the start of the dermatosis
Knowledge of the localisation of the lesions at the start of the problem is essential since numerous dermatoses exhibit a preferential topography:
• Otitis, pododermatitis in atopic dermatitis,
• Dorsolumbar pruritus in flea allergy dermatitis,
• Elbows, free margin of the ear pinna with sarcoptic mange,
• Abdomen with superficial pyodermatitis (impetigo),
• Scrotum with contact allergy,
• Periorificial zones with disorders of zinc metabolism.
K) Response to previous treatments
The most important aspect is their efficacy over time. Dose rates and durations of treatments are checked.
The response to steroid therapy is good in flea allergic dermatitis, superficial pyoderma, atopic dermatitis, and in the early stages of food allergies; it is partial or poor in chronic food allergies, demodectic mange, or Malassezia dermatitis.
The flea control strategy should be thoroughly and critically analysed. The latter is an essential element for diagnosis (exclusion of the diagnosis of FAD or louse infestation) and for the implementation of anti-parasitic control. The correct use of topical treatments is another element that is often overlooked.
Some shampoos are used repeatedly despite the fact that they provoke cutaneous inflammation at each use. Topical corticosteroids are sometimes used in large quantities, promoting the emergence of cutaneous infections.
Recording the administration of any medication is a useful way of determining causative agents if a toxic dermatitis is suspected or to diagnose cutaneous calcinosis following prolonged corticosteroid administration.
L) Contagious nature
If there is apparent contagion (human or animal), the diagnosis is restricted to the detection and identification of sarcoptic mange, cheyletiellosis, dermatophytosis, or a massive flea infestation in the environment.
1. Dysart LM, Coe JB, Adams CL. Analysis of solicitation of client concerns in companion animal practice. J Am Vet Med Assoc. 2011 Jun 15;238(12):1609-15.
2. Picco F, Zini E, Nett C, Naegeli C, Bigler B, Rufenacht S, et al. A prospective study on canine atopic dermatitis and food-induced allergic dermatitis in Switzerland. Vet Dermatol. 2008 Jun;19(3):150-5.