Atopic dermatitis or eczema is an inflammatory skin disease
which often occurs in the skin creases (backs of knees, elbow creases, armpits,
neck and on the face). Atopic dermatitis is characterised by itchy, red, dry
and/or cracked skin eruptions. It is a chronic (long-term) condition that is
not contagious, but the a tendency to have the condition is genetic .The
condition affects males and females equally, affecting 15-20% of school
children and 2-3% of adults in the UK as around 65% of cases clear up by age
16. Prevalence of atopic dermatitis symptoms has increased over the last ten
years, perhaps due to the increased use of soaps, detergents and frequency of
bathing as well as better diagnosis and more awareness.
The symptoms of atopic dermatitis can vary depending on
severity of the condition, mild eczema often involves small areas of dry skin
that are often itchy. Eczema in the skin creases is said to have a flexural
pattern, but other visual symptoms include coin sized areas of
inflammation/rash (a discoid pattern) or bumps of inflammation in hair
follicles (follicular pattern). Peaks of severity of symptoms are known as
flare-ups and skin often becomes very itchy, hot, red and inflamed; because of
scratching the skin can bleed or weep and become swollen; skin is also
susceptible to staphylococcus aureus infection and impetigo. Repeated
scratching can lead to lichenification where the skin is hard and even itchier.
Suffers of atopic dermatitis have a decreased barrier
function of the skin, the largest organ of the body, which has the normal role
to protect the internal organs of the body from infection and toxins. The loss of this function causes an
exacerbation of the Th2 allergic immune response and changes to the lipids
(fats) and so the loss of water from the skin tissue. This change is due to
abnormal filaggrin expression, filaggrin is a protein which binds to keratin
fibres in epidermal (the top layer of skin) cells and encourages the
activities of lipid producing enzymes. Filaggrin affects the keratinocytes
(skin cells), making them flatten and so affects the amounts of lipid
surrounding the cells and how tightly packed the cells are together (this
can also be caused by changes in skin pH (acidity) which is linked to filaggrin
expression). This increases the permeability of the skin
and increases the number of allergens and pathogens that can penetrate the skin. The inflammation in eczema is
due to an allergic response of immune cells, T-lymphocytes (white blood cells).
By allowing more allergens into the skin a more severe response occurs and by
allowing more pathogens, there is an infection risk and also more immune cells
migrate to the skin, so again reactions are severe. Scratching the skin
also attracts neutrophils another type of immune cell which secretes a lipid
called leukotriene B4, triggering T-lymphocytes and cause inflammation
(blocking the production of this lipid or the immune cell receptors can prevent
the development of an eczema reaction in mice).
The loss of the skin barrier function is thought to be due to problems in the gene for Ctip2, which is responsible for controlling synthesis of lipid in the skin and suppresses a protein called TSLP which triggers inflammation, when the gene is faulty, it could lead to skin complaints such as atopic dermatitis.
Th2 cells are a type of T lymphocyte involved in allergic
reactions and produces IgE antibodies which cause redness and itching (as well
as inhibiting TH1 cells). Scratching damages skin cells opening them up to
infection and causing them to secrete chemical messengers encouraging Th2 cells
to migrate to the area and cause inflammation. Our immune system develops in
the first 6 months of life, and this is when atopic dermatitis symptoms usually
manifest, in some people there is an imbalance of Th1 (immunity against
infection) and Th2 (immunity against allergens and parasites) cells. People
with atopic dermatitis often have Th2 dominance whereas those with TH1
dominance suffer from diseases such as rheumatoid arthritis, MS and Type 1
Diabetes. Due to this TH2 dominance, people with atopic dermatitis are also
likely to have asthma, hay fever and allergic rhinitis, however, some people
believe that through eczema and so being exposed to allergens that get into the
skin is actually what causes sensitivity and lead to these conditions.
Atopic
dermatitis flare ups can be caused by many factors. Rough clothing, dry
weather, soaps and detergents may irritate the skin; dust, pet hair and pollen
may trigger allergic reactions, as might food allergens such as nuts or dairy
products. Exercise or hot weather can cause problems due to sweat in the area
where eczema is most common. Stress is known to be a trigger of eczema, as are
hormonal changes in women, especially in pregnancy (around half of pregnant women
who suffer from atopic dermatitis feel their symptoms worsen). Environmental
factors such as changes in the seasons and hard/soft water can cause changes to
the skin and affect atopic dermatitis.
For people with atopic
dermatitis, psychological support may be needed, for people with severe skin
irritation, especially in visible areas. In children bullying is a common
problem for people with eczema as are self-confidence problems associated with
poor self image. In addition, the itchiness of atopic dermatitis can often
interfere with sleep which affects concentration and mood; this can have an
impact on a child’s school performance, which again can lead to self-confidence
issues.
One of the first
steps in treating atopic dermatitis is to have a skin test and blood tests, to
identify any particular allergies and so plan preventative measures (e.g. I am
allergic to grass pollen, so stay inside when grass has been recently mowed). As
well as avoiding triggers there are other things that can be done at home,
keeping nails short to prevent scratching that can lead to infection, wearing
loose fitting clothing of soft fabric, keeping the house free from dust mites
and avoiding strong detergents.
Treatment includes emollients which are important
in keeping skin moist and can be used liberally all the time (if skin is very
dry, should be used every 2/3 hours). Emollients provide a protective film over
the skin, this prevents water loss. Emollients are often used after bathing to retain
the moisture of the skin. There are many types of emollient, some can be
brought over the counter and other prescribed, there are some emollients which
can be used a soap substitutes and others to add to bath water. Emollients
should be used throughout the year, not only during flare ups, but can over
time become ineffective. Emollients should not be shared with other and should have
applicators or a pump dispenser in order to minimise infection. During a flare
up, emollients should be used very frequently, alongside anti-inflammatory
treatment.
When skin is inflamed, topical corticosteroids
can be applied directly to the skin; however different strengths may need to be
applied to different areas of the body (i.e. milder treatment for the face and
strong ointments for flare ups). This treatment should not be used for more
than several weeks (a sign that stronger treatment may be needed) and used a
maximum of twice daily (applied half an hour after applying emollient to the
affected area). Corticosteroids are measured in fingertip units (see below) which, as they
must be spread thinly, can cover a large area of skin. When applied, they can
often sting or burn and are not suitable for long term treatment as can have
side effects such as thinning of the skin (especially around creases), acne,
increased visibility of blood vessels (in particular the cheeks) and increased
hair growth on the skin.
Other treatments include antihistamines
which can reduce the itching associated with atopic dermatitis as they prevent the
release of histamine which triggers allergic responses when in contact with
allergens, some antihistamines are sedating and cause drowsiness, these are for
short term use only and people should not drive or operate heavy machinery when
on this treatment. Similarly topical immunosuppressants reduce the immune
response to a particular area. For severe flare-ups, oral corticosteroids can
be prescribed to reduce inflammation (these also are used to treat asthma). The
course of treatment is about two weeks long, one tablet a day. This medication
can have severe side effects if used for an extended period of time, such as
hypertension (high blood pressure), osteoporosis (easily broken bones), fluid
retention (and so swollen ankles/legs) and in children can affect their growth.
To prevent scratching and allow the skin to heal, medicated dressings (which
also prevent itchiness) are used but only on uninfected skin. If the skin
becomes infected usually antibiotic treatment is prescribed, this is usually
tablets, but could involve antibiotic creams applied to the infected area. If
infected with herpes simplex virus (which causes cold sores) antiviral
treatment will be given. In the long term, people prone to infection use
antiseptic creams, as antibiotic treatment could lead to resistance. Dermatologists
could also offer phototherapy which involves ultraviolet light to treat the affected
area.
There is currently no cure for eczema,
however new studies into the genetics behind skin problems could lead to
epigenetic cures in the future and there are many treatments that can alleviate
or control the symptoms. In the majority of cases, children ‘grow out’ of
eczema and their symptoms subside naturally in their teenage years.
No comments:
Post a Comment