Scratching & Itching in
Dogs
Overview:
 Scratching
is a common complaint to affect dogs. Most people
associate scratching in dogs with fleas. While fleas are often
the cause of this, there are many other possible causes for
scratching & itching in dogs.
Fleas:
Fleas are a common
problem in dogs. They are most abundant in the summer months,
although in tropical areas may be found all year around. Signs
of dog fleas include seeing small, black insects in the coat,
grit like appearance in the dog's bedding & scratching.
If your dog has
fleas, you will have to treat both the dog & your home. Your
veterinarian will be able to advise on the best product to use
on your dog. There are many excellent products on the market for
dogs, many of which are applied to the back of the neck. The
environment will either need to be treated with a flea bomb
or a pest controller, along with some thorough washing &
vacuuming.
Flea Allergy
Dermatitis:
While the odd flea
on most dogs won't bother them too much, some dogs will be
hypersensitive to them. This is known as Flea Allergy Dermatitis
(also known as flea bite hypersensitivity).
As the name
suggests, it is caused by an allergic reaction to a flea bite.
There are 15 known allergens in flea saliva, each one is capable
of causing an allergic reaction in the dog. Just one bite from a
flea is enough to trigger an allergic reaction in your dog.
Some symptoms
include: frequent scratching & biting of the fur, especially on
the back & the base of their tail. Other symptoms of flea
allergy dermatitis include raised bumps (papules) or scabs on
the skin & thinning fur in the affected area.
Your veterinarian
will be able to diagnose flea allergy dermatitis. This can be
done visually. Signs of fleas on your dog are a good indicator.
However, extremely sensitive dogs will have few if any fleas on
them. This is due to excessive self grooming. In such cases,
to get a definite diagnosis that your dog is in fact allergic to
flea bites & not something else then a intradermal skin testing
is required.
Treatment
involves:
- Eliminating fleas from your
dog & environment, and preventing re-infestation of
fleas.
- Treating
secondary skin infections caused by excessive biting &
scratching of the skin. This may involve a course of
antibiotics, medicated shampoo & or a topical medication.
-
Antihistamines or steroids may be prescribed by your
veterinarian to control inflammation & reduce itching.
-
Hyposensitisation
(desensitisation). This involves injecting minute amounts of
flea antigen into the dog in the hope that it will
re-programme the immune system so it's not hypersensitive to
flea antigen.
Mites:
Mites are tiny
members of the arachnid (spider) family.
There are several
types of mites in dogs including Notoedric Mange,
Cheyletiellosis (walking dandruff), Lynxacariasis, Trombiculidiasis
(chiggers) & Otodectic Mange (ear mites). Most of
these are fairly rare in the dog so I won't go into detail.
Ear mites (Otodectes
cynotis): Although the name would suggest otherwise, ear
mites can live on any part of the body although they generally
live in the ears of dogs. They are the most common cause of otitis externa (inflammation of the outer ear canal) in
dogs.
Not all dogs will
display symptoms of ear mites but often they will scratch at
their ears & or shake their heads. Other symptoms may include
reddish/brown discharge in the ear, bleeding from the ear,
coffee-grounds like appearance in the ear, scratch marks, odour.
Treatment depends
on how severe the problem is. Removal of the exudates from the
ear by instilling a few drops of mineral oil & gently massaging
the base of the ear. This will loosen the exudate, which will
make it easy to remove.
Mange is a highly contagious,
intensely itchy skin disease, caused by the Sarcoptic mange.
The first sign of
sarcoptic mange is usually intense pruritus (itching)
along with hair loss & a thick/crusty & scabby appearance to the
skin, especially along the tip of the ears. It then progresses
to the face & neck, & if untreated can progress to other parts
of the body.
Scratching the
affected areas causes the skin to become raw, red & inflamed,
which can cause potentially dangerous secondary bacterial
infections.
Diagnosis is made by taking a scraping of the
dog's crusty skin examine it under a microscope for the presence
of mites or mite eggs.
Treatment
involves:
-
Semi &
longhaired dogs may need to be clipped. Cleansing of the area
to soften thick crusts, followed by a weekly lime sulfur dip.
- Amitraz has
been shown to be another successful dip, this product hasn't
been approved for use on dogs though.
- Ivermectin.
This is given by injection. It hasn't been approved for use in
dogs, although reports are that it is safe.
- Revolution:
This product is typically a flea & worm product but has shown
to be effective on sarcoptic mange.
Cheyletiellosis (also known as
walking dandruff) is a highly contagious skin disease cause
by the Cheyletiellosis mite. Young dogs are more often
infected although dogs of any age can have these mites.
Symptoms include
pruritus (itching), excessive scaling/dandruff, crusting along
the back.
Cheyletiellosis is diagnosed by
flea combings, skin scrapings, fecal flotation or
acetate tape preparations.
Treatment may
include; lime sulfur or pyrethrin dips & or Ivermectin.
Allergies:
The word allergy
means 'altered working'. Just like humans, dogs can have
allergies too. Allergies are a common cause of skin disease in
dogs.
The purpose
of the immune system is to keep infectious microorganisms, such
as certain bacteria, viruses, and fungi, out of the body, and to
destroy any infectious microorganisms that do invade the body.
Allergies are caused by an inappropriate response to a substance
which would usually be considered harmless.
In an allergic
animal, the immune system over reacts to the substance & mounts
an immune response against it.
In dogs there are
four types of allergies;
insect (most often caused by fleas, but occasionally
mosquito bites can cause an allergic reaction),
food, contact & inhalant.
All the above
causes have different symptoms, most of which are already
covered in specific articles but scratching is often seen in the
case of allergies.
Food Intolerance:
A food intolerance
is an adverse reaction to a food, one of it's ingredients or
additives. It differs from a
food allergy in that the immune system is not involved. Food
allergies typically cause non seasonal itching, especially
around the head & face, swollen & inflamed areas on the face &
ears, hair loss due to itching, vomiting & diarrhea.
A common food
intolerance that many people have heard of is milk. This is
because many mammals lack the enzyme necessary in order to
digest the lactose in, which is the major sugar in milk.
The most common
causes of food allergies & intolerances in dogs are fish, beef,
eggs, wheat & milk. Dogs can become allergic & intolerant to
foods they have eaten for a long period of time.
As you can see
above, vomiting & diarrhea are symptoms which can also be
displayed in a dog who is allergic to a food, however the
allergic dog also has other symptoms such as itching, which is
caused by the immune response.
Avoiding the food
which caused the intolerances is the best method of treatment.
This may either be a home made diet or a commercial one. If you
are feeding a home made diet it is important to ensure that your
dog is receiving the correct nutrients in the diet.
Ringworm:
Ringworm is the
most common fungal skin infection seen in dogs. Contrary to the
name, ringworm is caused by a microscopic group of parasitic
fungal organisms known as dermatophytes (which means "plants
that live on the skin"). Ringworm invades the dead, outer layers
of the skin, claws & hair.
The most
recognised sign your dog is infected with ringworm is circular
patches of hair loss, especially around the head & limbs
(although it can occur on other parts of the body also). Other
signs are grey, patchy areas of baldness, with or without
redness & itching, seborrhea sicca (a type of dandruff),
dry/flaky skin, onychomycosis (infection of the claw & clawbed).
Other causes of itching &
scratching in dogs include;
- Damp hay itch
- Lice
- Lick granuloma
- Maggots
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