Senile pruritus

In the elderly, xerosis, is the most common cause for an itch due to the degradation of the skin barrier over time.[4] The skin barrier is critical for protecting the body from external pathogens, maintaining body temperature as well as other homeostatic or baseline functions. Over time, as the skin ages, the permeability barrier function begins to decline leading to dry skin. Reduced structural protein levels, lipids, as well as other critical enzymes that contribute to a strong epidermal(skin) barrier as seen overtime when compared to young skin.[4] Skin surface pH changes can also lead to chronic itch. Many properties that are needed for a functional barrier must reside at a more acidic pH, however, aged skin tends to be accompanied with an basic increase in pH. Disruptions in the pH gradient not only induce itch signaling but contribute to the overall decline in barrier function.[8] These intrinsic alterations leads aged skin to be more at risk for irritant exposure. Ultimately, the vulnerable barrier increases the risk of developing pruritus and other skin diseases.

Another cause of senile pruritus may include neurological changes in the body as it ages. An itch is triggered by both the peripheral and central nervous system in response through a complex circuit of neurons. Specifically, c fibres and Aδ fibres are responsible for the itch response which have been seen to be inhibited at higher rates in the elderly.[3] In addition to neurological inhibition, skin hydration can have an effect on the nervous system circuit. Skin moisture keeps the barrier function intact, but reductions can lead to a decrease in the itch threshold needed to be reached.[3]

Immunosenescence occurs over time where the immune system undergoes changes that may impact both the innate and adaptive immune systems.[8] These alterations may lead to increased immunoreactivity to intrinsic and extrinsic stimuli that can cause the body to become more sensitive and reactive. This may result in the form of an itch when exposed to stimuli that the body was not reactive to in the past. The immune system is responsible for a myriad of activities to defend the body from foreign substances via various endogenous and exogenous pathways. Within the lymphatic system, the thymus gland produces T cells that aid the immune system to recognize and attack potential harmful stimuli. In the case for the aging population, the thymus gland undergoes physical and chemical conformational changes that reduce the organ's size and therefore impacting its function to produce T cells.[8] This impairment may lead to decreased Th2 cells responsible for anti-body response when encountering allergens, bacteria, toxins, and other irritants, which may lead to an increase in autoreactivity-causing senile pruritus.[9]

Topical treatments may be used to reduce inflammation and the painful or itchy sensation or flare-ups locally at the site on the skin. Topical treatments are typically safe for the geriatric population.[12][13]

Topical treatments may include:

• corticosteroids
• immunomodulators
• menthol
• local anesthetics

The medication benefits and risks of systemic treatments are reviewed for elderly people suffering with pruritus due to various reasons, like underlying conditions.[12]

First generation anti-histamines can be useful due to their sedating qualities in treating pruritus. Second generation anti-histamines are used to treat allergies and can help reduce the inflammation in treating pruritus. Compared to first generation anti-histamines, second generation anti-histamines are typically non-sedating. However, they may not be used in elderly people because of their anticholinergic effects, like constipation and dry mouth.

Some common anti-histamine medications may include:

• diphenhydramine, most commonly known as Benadryl
• loratidine, most commonly known as Claritin
• cetirizine, most commonly known as Zyrtec

Immunosuppressants have seen use at low doses along side systemic steroids and phototherapy for chronic symptoms of senile pruritus or dermatitis. Senile pruritus could have connections to the loss of tolerance for antigens on the skin that result from aging skin, which can potentially lead to other autoimmune disorders like bullous pemphigoid.[14]

Immunosuppressive medications may include:

• methotrexate, immunosuppressant and agent used in chemotherapy
• azathioprine, immunosuppressant used as treatment in various conditions, such as an anti-rejection medication in kidney transplant patients
• mycophenolate, immunosuppressant agent used in conditions, such as organ transplants and autoimmune diseases

Anticonvulsants have also found use as a substitute for oral antihistamines to treat senile pruritus, and can be adjusted accordingly to individual needs and characteristics.[11]

Antidepressants and Opioid agonists/antagonists are also drug classes that may help dampen the itch response in people with pruritus.[13] Opioid antagonists have shown to be effective in relieving pruritus as well due to their antagonizing effects on receptors within the central nervous system. Psychotropic agents work very similar to anti-histamines for those who cannot use the latter.[6]

Topical salicylic acids and cannabinoids have been used for pruritus as well, though their pathway is not clearly known and need more studies before this can be shown as a safe and viable treatment.[13]

Removing or avoiding certain stimuli in the surroundings that could potentially induce or exacerbate the itch are shown to be effective.[13] This includes avoid wearing clothing such as wool, nylon, latex, and other synthetic materials. Bathing in warmer water can inhibit the itch sensory fibers. Non-invasive brain stimulation, often used to treat neuropsychiatric conditions, has shown to be successful in repressing the itch cycle.[15] The device works by sending electrical currents that can redirect how the signaling cascade is fired through the peripheral and central nervous systems.

Phototherapy can be considered under the guidance of a dermatologist. UV light phototherapy has been used to treat various pruritic symptoms such as pruritus resulting from renal disease, eczema, or just of unknown origin.[11]

Usually used for temporary symptom relief and may decrease the severity of the itchiness. Cooling agents work as emollient replacements as dry, aged skin tend to lack the skin's natural emollients. Cooling agents like urea-based formulations help attract water into the skin, restoring the skin's hydration status.[16] Using refrigerated topical products may also be an option for additive cooling effects.

Bathing for 15 minutes in a warm bath followed by applying a mixture of a topical steroid and heavy moisturizer (Aquaphor, Eucerin, etc.) may improve the moisture retention of the skin and helps with symptom relief.[17] Wrapping can be done onto the wet skin to maintain effectiveness of the treatment.

Certain materials can promote further pruritus and can be avoided to minimizes itchiness or reaction, so it may be helpful to decrease contaxt with wool and synthetic material. Soap-free substitutes are available to avoid any soap-related irritations to the skin. Avoiding the overuse of heating in the winter. Having a humidifier can increase humidity and allowing skin to be less dry in the cold and dry seasons. Shorter fingernails can also help to minimize scratching and reducing chances of bacterial infection.[18]