What is allergy?
Allergy is a hypersensitivity disorder in which the body's
immune system overreacts to normally harmless environmental
substances known as allergens. People with allergies usually have
symptoms typical of Hay Fever or asthma. Comparatively, small
animals usually show signs of allergies on their skin and/or ears.
Horses may display signs similar to both people and small
Can animals get allergies? If so, how will I know?
Yes, animals can have allergies just like humans with either
seasonal or year-round signs. However, animals typically display
signs of allergies on their skin and/or ears. For instance, people
with allergies tend to sneeze and wheeze due to allergic rhinitis,
sinusitis, and asthma whereas allergic animals tend to itch and
scratch due to allergic inflammatory skin and ear disease. In
addition to itch, horses may have recurring hives and
"heeves/heaves". As the skin/ears become inflamed, secondary
infections (bacteria and yeast) develop leading to an even more
heightened state of itch experienced by the pet. Dander
(seborrhea), odor, red bumps (papules), pimples (pustules),
blackheads (comedones), scabs (crusts), red skin (erythema), skin
thickening (lichenification), and hair loss (alopecia) are signs
suggestive of allergies complicated by secondary infections.
Hives in the form of 'rings' in an allergic horse.
What are some things animals tend to be allergic to?
- Fleas (#1 allergy)
- Pollen (e.g., tree, grass, weed)
- Mites (e.g., house dust and storage mites)
- Insects (a common culprit in horses)
How do I know if my pet is itching too much?
Licking, chewing, biting, rubbing, and scratching are all signs
of pruritus (itch). Many times animals are itchier during the night
when they are not preoccupied with other events. The face, ears,
paws, armpits, groin, and rump tend to be the itchiest areas in
allergic small animals. Nevertheless, it can be difficult to
determine if a cat is itchy or just grooming. If a cat vomits
hairballs, has excessive hair in the stool, has areas of hair loss,
or has obvious skin lesions, the cat is likely to be itchy. Horses
may bite, rub themselves (against stalls, fences, etc.), flick
their tail, stomp their feet, and shake their head. The face, ears,
mane, underside of the trunk, limbs, and tail base are many times
the itchiest areas. Every pet has its own itch tolerance which
means the intensity and reason(s) for your pet's pruritus may not
be the same as a friend's pet.
Itchy allergic skin disease in a cat.
What are "secondary infections?"
Animals with underlying allergies often get secondary problems
in the form of infections. Bacteria and yeast (fungus) already
normally present on the skin (and in the ear) overgrow and cause
infection when the skin (ear) is not properly functioning as is the
case with allergies (and a multitude of other underlying skin
disorders). Skin inflammation due to allergies favors these
infections thereby complicating the clinical picture of the pet.
Often these infections add to the overall itch sensation and are
responsible for many of the skin changes-- dander (seborrhea),
odor, red bumps (papules), pimples (pustules), blackheads
(comedones), scabs (crusts), red skin (erythema), skin thickening
(lichenification), and hair loss (alopecia). Controlling these
infections with topical and/or oral antibacterial and antifungal
medication along with managing the underlying allergy will help
alleviate itch and secondary skin changes. Even the best managed
allergic animal will occasionally flare with an infection.
Therefore, owners/guardians should routinely look for signs of
infection on their allergic pet as infections just add to the
LEFT: Bacterial skin infection.
RIGHT: Yeast skin infection.
If my pet only seems itchy during a specific time of year,
should I be concerned?
It depends. Mild itch that is accepted as tolerable by an
owner/guardian may need no therapy other than timely baths. Itch
that is more intense or becomes more intense each year warrants a
discussion with your primary care veterinarian. Therapy in this
circumstance may include flea prevention (fly spray or spot-on for
horses), medicated shampoo, antibiotics, anti-yeast medication,
antihistamines, a fatty acid supplementation, and/or a short course
of oral or topical steroids. If this approach does not help
alleviate signs, the pet does not tolerate it, or if the itchy
season is lengthening then consultation with a dermatologist is an
option. Regardless who examines your pet, it is important to start
managing these pets sooner rather than later.
How soon can I expect for my pet's allergic skin disease to get
With dermatology there is no such thing as a "quick fix" because
it takes time to understand the underlying cause of your pet's
condition. Often the skin condition has been present for many years
prior to referral necessitating an ample period of time to improve
and manage skin signs. First, we will need to eliminate the
"absolutes" which are infections (bacteria and yeast) and
flea/insect bites. Since therapy for allergies is tailored to the
individual, other diagnostic tests and therapies are on a case by
case basis. It is important to remember that allergies are managed,
not necessarily cured!
What is skin testing?
Intradermal testing (IDT) or allergy skin testing is a tool that
aids the dermatologist in the selection of environmental allergens
(pollen, mold, mites, insects, dander) for subsequent immunotherapy
(allergen-specific allergy shots or oral allergy drops). This test
followed by tailor-made allergy shots or oral drops is best
performed after other possibilities for the itchy skin disease have
been excluded. Veterinary IDT is similar to human allergy skin
testing; however, our patients need sedation and clipping most of
the time. The side of the chest (neck for horses) is shaved in the
shape of a rectangle and small black Sharpie pen dots are made in a
linear array on the shaved skin allowing the dermatologist to know
where to make each injection. A panel of allergens (pollen, mold,
mites, insects, dander) is then injected in the skin. The size of
any developing wheals is recorded. The entire procedure lasts
approximately 30 minutes in small animals, while in horses test
reading takes a full 24 hours (overnight stay). Importantly, this
test is used for environmental allergies (atopic dermatitis), not
Is there a benefit to allergy skin testing?
Yes. Intradermal testing allows us to select allergens (pollen,
mold, mites, insects, dander) to which the pet is allergic to for
immunotherapy (allergy shots or oral allergy drops) administration.
These injections or oral drops are the best long-term management
strategy for most pets with environmental allergies since they are
directed toward improving the underlying cause of signs.
Specifically, this form of therapy is designed to de-sensitize your
pet's skin to common every day allergens. However, immunotherapy
does not exclude the continued use of topical therapies and routine
monthly flea prevention in allergic pets. In general, pets
experiencing clinical signs (itchy skin/ears and recurring
infections) for at least 5-6 months out of the year benefit the
most from this form of testing.
What medications need to be discontinued prior to skin
There are several medications prescribed for itchy skin that
will inhibit (wheals) on allergy skin testing. Please keep in mind
this is a rough guideline; individual cases may vary. Review the
drug withdrawal schedule below and discuss it with your primary
care veterinarian. Drugs are to be withdrawn under the advice and
discretion of your primary care veterinarian.
|Topical steroids (ears, skin, or eyes)
||15-30 days (2-4 weeks)
||30-60 days (4-8 weeks)
||70-84 days (10-12 weeks)
|Topical or oral antihistamines
||10-14 days (2 weeks)
|Fatty acid supplementation (if
||14-21 days (2-3 weeks)
||2-3 days (0.5 weeks)
||Case by case basis
What medications can I continue to give my pet prior to skin
Antibiotics, antifungals, flea prevention (fly spray for
horses), heartworm prevention, insulin, thyroid supplementation,
heart medication, anti-seizure medication, and ophthalmic
cyclosporine/tacrolimus for dry eye can be continued prior to any
appointment or skin testing procedure. Cool water baths with
oatmeal can be used to help soothe the skin and relieve itch up to
3 days before skin testing. Ears may be flushed with a
veterinarian-recommended flushing agent. Please discuss what
medications you should continue administering prior to the
appointment with your primary care veterinarian in the event your
pet has not yet been examined by the dermatologist.
When is the best time to skin test?
Skin testing can usually be performed throughout the year;
however, pets with seasonal allergies are best tested near the end
of their "allergy season" (30-60 days from peak season).
Intradermal testing at other times of the year for seasonally
allergic pets may require repeat testing. Consequently, many pets
will not be skin tested during the initial appointment as the
seasonal history needs to be ascertained and complicating
infections need to be eliminated.
What is blood (serum) allergy testing?
Blood allergy testing is usually reserved for cases in which
skin testing cannot be performed. This scenario occurs when an
animal cannot be sedated due to another medical condition or when
appropriate drug withdrawal (e.g., steroids) cannot be
accomplished. Most dermatologists would agree that intradermal
testing (IDT) gives a better reflection of what the skin is
reacting to compare to blood allergy testing. Since feline skin
does not visibly react as well as other species during (IDT), blood
allergy testing may be recommended for allergic cats. Sometimes
both tests are used to get a better overall assessment of which
environmental allergens are bothersome to the pet. Interpretation
of blood allergy tests is improved once other causes of itchy skin
disease have been excluded (especially year-round itchy pets).
Importantly, this test is used for environmental allergies (atopic
dermatitis), not food-related allergies.
How long does it take to see improvement with allergy
injections or oral allergy drops?
Most pets will respond to immunotherapy (allergy shots or oral
allergy drops) within 6-9 months, but some will require up to a
year before total benefits are appreciated. Roughly 50-80% of
animals with environmental allergies (atopic dermatitis) respond to
this form of therapy, but response does vary. During the initial
phase of immunotherapy ("induction") most pets will require
symptomatic treatments (e.g., medicated baths, antihistamines,
steroids, cyclosporine) to make them more comfortable. Over time
the hope is to reduce the frequency or need of some of these other
medications. Please remember allergies are managed and rarely ever
cured. Our goal is to reduce 80-90% of the itch/clinical signs,
80-90% of the time.
How do I know if my pet has food allergies?
Animals presenting with itchy allergic skin disease can look
very similar if not identical regardless of the "trigger" (pollen,
mold, mites, insects, dander, food). This why the animal's history
of itchy skin disease is important as it can provide clues to
potential triggers. Animals reacting to foodstuffs tend to have
year-round itch assuming they are eating roughly the same diet all
year long. Horses with food allergies may have recurring hives as
well. In this instance, a veterinarian may recommend an exclusive
novel diet (to which the animal has never been exposed) for a
period of time in order to determine if food is a component of the
signs. If clinical signs improve with the change in diet, then the
pet is challenged with the previously fed diet to determine if itch
returns. Recurrence of itch after diet challenge confirms the
diagnosis of food allergy (cutaneous adverse food reaction).
Currently skin testing or blood (serum) allergy testing is not
recommended to support a diagnosis of food allergies since these
tests have many false results.
Can I just treat my pet with steroids?
Steroids (e.g., prednisone) definitely have their place in the
treatment of allergic skin disease, and are often used to alleviate
itch. However, long-term use of steroids can cause detrimental
health problems. For this reason, it is recommended the underlying
trigger of allergic signs be sought and managed with other less
harmful treatments for those animals with chronic problems.