10. Dermatology and Skin Disorders: A Complete Guide to Psoriasis, Scabies, and Eczema

DERMATOLOGY AND SKIN DISORDERS: A TEACHER’S COMPREHENSIVE GUIDE TO PSORIASIS, SCABIES AND ECZEMA

Welcome, future pharmacists and healthcare professionals!

As a pharmacotherapeutics educator with years of experience teaching dermatology, I have observed that skin disorders are among the most common conditions encountered in clinical practice. Our skin is the largest organ of the body and is constantly exposed to environmental factors that can lead to various disorders. Skin conditions such as psoriasis, scabies, and eczema are quite common and can significantly affect comfort, appearance, and quality of life. Many patients suffer from these conditions for years without adequate treatment because they do not fully understand their condition or the available management options.

In this comprehensive guide, I will take you through three major skin disorders: Psoriasis, Scabies, and Eczema. We will explore their types, causes, symptoms, diagnostic approaches, and evidence-based management strategies. By the end of this article, you will have the knowledge and confidence to counsel patients effectively, recognize red flags, and contribute to better dermatological outcomes. Let us begin.

PART 1: PSORIASIS

What is Psoriasis?

Psoriasis is a chronic autoimmune skin condition in which the immune system mistakenly attacks healthy skin cells. This causes rapid multiplication of skin cells, resulting in thick, red, scaly patches known as plaques. Normally, skin cells grow and shed in a cycle that takes about a month. In psoriasis, this process is accelerated to just a few days, causing a buildup of cells on the skin’s surface.

Psoriasis affects approximately 2-3% of the global population and can occur at any age, though it most commonly appears between the ages of 15 and 35. The condition is not contagious and cannot be spread from person to person. While there is no cure for psoriasis, various treatment options can effectively manage symptoms and improve quality of life.

Types of Psoriasis

Psoriasis can present in several distinct forms:

• Plaque psoriasis: The most common type, accounting for about 80-90% of cases. Characterized by thick, red patches covered with silvery scales, typically on the elbows, knees, scalp, and lower back.
• Inverse psoriasis: Appears as smooth, red, inflamed patches in skin folds such as the armpits, groin, and under the breasts. It is often worsened by friction and sweating.
• Guttate psoriasis: Characterized by small, drop-shaped lesions that often appear suddenly after a bacterial infection, particularly streptococcal throat infections. It is more common in children and young adults.
• Pustular psoriasis: A rare and severe form characterized by pus-filled blisters on the hands and feet. It can be triggered by infections, stress, or certain medications.
• Erythrodermic psoriasis: A severe, life-threatening form that affects large areas of the body, causing widespread redness, scaling, and pain. It requires immediate medical attention.

Causes and Triggers of Psoriasis

Psoriasis has a genetic basis and is influenced by the immune system. Several external factors can trigger or worsen psoriasis flare-ups:

• Stress: Emotional stress can trigger or exacerbate psoriasis symptoms.
• Skin injury: Any trauma to the skin, including cuts, scrapes, or sunburn, can trigger psoriasis at the site of injury (Koebner phenomenon).
• Infections: Bacterial and viral infections, particularly streptococcal throat infections, can trigger guttate psoriasis.
• Cold weather: Dry, cold weather can worsen psoriasis symptoms.
• Certain medications: Drugs such as lithium, antimalarials, and beta-blockers can trigger or worsen psoriasis.
• Smoking and alcohol consumption: Both are associated with increased severity of psoriasis.

Symptoms of Psoriasis

The symptoms of psoriasis can vary depending on the type and severity of the condition. Common symptoms include:

• Red, inflamed skin patches covered with silvery scales
• Itching, burning, or soreness in affected areas
• Dry, cracked skin that may bleed
• Thickened, pitted, or ridged nails (nail psoriasis)
• Swollen and stiff joints (psoriatic arthritis)
• Scalp involvement with flaking and itching

Management of Psoriasis

Non-Pharmacological Management

Non-pharmacological measures are essential for managing psoriasis:

• Regular use of moisturizers to reduce dryness and scaling
• Avoiding triggers such as stress, skin injury, and infections
• Maintaining a healthy weight and lifestyle
• Sun exposure in moderation (phototherapy can be beneficial)
• Stress reduction techniques such as meditation and yoga

Pharmacological Management

Several classes of medications are used to treat psoriasis:

• Topical corticosteroids: Reduce inflammation and itching. Available in various strengths depending on the severity and location.
• Vitamin D analogues: Slow down skin cell growth (e.g., calcipotriene, calcitriol).
• Topical retinoids: Derived from vitamin A, reduce inflammation and scaling.
• Phototherapy: Ultraviolet light therapy (UVB or PUVA) under medical supervision.
• Systemic drugs: Used for moderate to severe psoriasis, including methotrexate, cyclosporine, and acitretin.
• Biologics: Targeted therapies that block specific immune system pathways (e.g., adalimumab, etanercept, ustekinumab).

PART 2: SCABIES

What is Scabies?

Scabies is a highly contagious skin infestation caused by the human itch mite, Sarcoptes scabiei var. hominis. The female mite burrows into the upper layer of the skin to lay eggs, causing intense itching and a characteristic rash. Scabies affects people of all ages and socioeconomic backgrounds and is commonly spread through prolonged skin-to-skin contact.

The incubation period for scabies is typically 2-6 weeks for first-time infestations. However, individuals who have had scabies before may develop symptoms within 1-4 days of re-exposure. Scabies is not a sign of poor hygiene—it can affect anyone, regardless of cleanliness.

Symptoms of Scabies

The classic symptom of scabies is intense itching, which is often worse at night. Other symptoms include:

• Severe itching, particularly at night
• A pimple-like rash with small red bumps
• Thin, grayish-white burrow lines on the skin (mite tunnels)
• Redness and inflammation in affected areas
• Common sites: Between fingers, wrists, elbows, armpits, waist, buttocks, and genital area
• In infants and young children, the rash may appear on the scalp, face, palms, and soles

Management of Scabies

Pharmacological Management

The treatment of scabies involves the use of topical scabicides:

• Permethrin 5% cream: The first-line treatment. Applied to the entire body from the neck down and left on for 8-14 hours before washing off.
• Antihistamines: Used to relieve itching (e.g., cetirizine, loratadine).
• Crotamiton cream: An alternative for patients who cannot tolerate permethrin.
• Ivermectin: Oral medication for severe or crusted scabies, or for patients who fail topical therapy.

Non-Pharmacological Management

Non-pharmacological measures are essential to prevent reinfestation:

• Wash all clothing, bedding, and towels in hot water and dry on high heat.
• Items that cannot be washed should be sealed in plastic bags for at least 72 hours.
• All household members and close contacts should be treated simultaneously to prevent reinfestation.
• Maintain good personal hygiene.

PART 3: ECZEMA (DERMATITIS)

What is Eczema?

Eczema, also known as dermatitis, is a group of conditions that cause dry, itchy, and inflamed skin. It is characterized by a weakened skin barrier, leading to increased water loss and susceptibility to irritants and allergens. Eczema is one of the most common skin conditions, affecting approximately 10-20% of children and 1-3% of adults worldwide.

The most common type of eczema is atopic dermatitis, which often begins in childhood and may improve or persist into adulthood. Eczema is not contagious and cannot be spread from person to person.

Symptoms of Eczema

The symptoms of eczema can vary depending on the type and severity. Common symptoms include:

• Dry, sensitive skin
• Intense itching, often worse at night
• Red, inflamed patches on the skin
• Cracked, scaly, or thickened skin (lichenification)
• Small, raised bumps that may leak fluid when scratched
• Common sites: Hands, face, neck, inner elbows, behind knees, and ankles

Causes and Triggers of Eczema

Eczema is caused by a combination of genetic and environmental factors. Common triggers include:

• Genetic predisposition: Family history of eczema, asthma, or hay fever
• Irritants: Soaps, detergents, chemicals, and solvents
• Allergens: Dust mites, pet dander, pollen, and certain foods
• Environmental factors: Dry air, cold weather, and sweating
• Stress: Emotional stress can trigger or worsen eczema flare-ups
• Skin infections: Bacterial, viral, or fungal infections

Management of Eczema

Non-Pharmacological Management

Non-pharmacological measures are the cornerstone of eczema management:

• Regular use of moisturizers and emollients to restore the skin barrier
• Avoiding irritants and known allergens
• Using mild, fragrance-free soaps and cleansers
• Taking short, lukewarm baths or showers
• Identifying and avoiding specific triggers
• Stress reduction and relaxation techniques

Pharmacological Management

Several classes of medications are used to treat eczema:

• Topical corticosteroids: Reduce inflammation and itching (various strengths available).
• Topical calcineurin inhibitors: Non-steroidal options for sensitive areas (e.g., tacrolimus, pimecrolimus).
• Antihistamines: Help relieve itching, particularly at night.
• Phototherapy: Ultraviolet light therapy for moderate to severe eczema.
• Systemic immunosuppressants: Used in severe cases (e.g., cyclosporine, methotrexate).
• Biologics: Targeted therapies for severe atopic dermatitis (e.g., dupilumab).

COMPARISON TABLE: PSORIASIS VS SCABIES VS ECZEMA

Feature	Psoriasis	Scabies	Eczema
Cause	Autoimmune, genetic	Mite infestation	Immune dysfunction, genetic
Contagious	No	Yes	No
Key symptom	Thick, scaly plaques	Intense itching (night)	Dry, itchy, inflamed skin
Common sites	Elbows, knees, scalp	Between fingers, wrists, genital area	Hands, face, neck, flexures
First-line treatment	Topical steroids, vitamin D analogues	Permethrin cream	Moisturizers, topical steroids
Requires long-term management	Yes	No (if treated)	Yes

A TEACHER’S CLINICAL INSIGHTS

Over my years of teaching dermatology and pharmacotherapeutics, I have developed a few key insights about skin disorders that I always share with my students:

• Psoriasis is a chronic condition that requires long-term management. Many patients need both topical and systemic therapies. Educate patients about the importance of adherence to treatment and regular follow-up.
• Scabies is often misdiagnosed because the itching can be confused with other skin conditions. Always consider scabies in patients with intense nocturnal itching and a rash in characteristic areas. Treat all close contacts simultaneously.
• Eczema management begins with moisturizers. Emollients are the foundation of eczema treatment and should be used even when the skin is clear.
• Patient education is essential for all skin disorders. Patients need to understand their condition, recognize triggers, and know how to use their medications correctly.

FREQUENTLY ASKED QUESTIONS (FAQs)

1. What is psoriasis?

Psoriasis is a chronic autoimmune skin condition characterized by rapid skin cell growth, leading to thick, red, scaly patches on the skin. It is not contagious.

2. What is scabies?

Scabies is a highly contagious skin infestation caused by the human itch mite. It causes intense itching, especially at night, and a characteristic rash with burrow lines.

3. What is eczema?

Eczema is a group of conditions that cause dry, itchy, and inflamed skin due to a weakened skin barrier. It is the most common skin condition in children.

4. Is psoriasis contagious?

No, psoriasis is not contagious. It is an autoimmune condition and cannot be spread from person to person.

5. How is scabies treated?

Scabies is treated with topical scabicides such as permethrin 5% cream. All household members and close contacts should be treated simultaneously to prevent reinfestation.

6. What is the difference between eczema and psoriasis?

Eczema typically presents as dry, itchy, inflamed skin in flexural areas and is associated with a weakened skin barrier. Psoriasis presents as thick, scaly plaques on extensor surfaces and is an autoimmune condition with rapid skin cell turnover.

7. Can eczema be cured?

There is no cure for eczema, but it can be effectively managed with moisturizers, topical treatments, and avoidance of triggers. Many children outgrow eczema as they get older.

SUMMARY

Skin disorders like psoriasis, scabies, and eczema require proper management with lifestyle care and medications to reduce symptoms and improve quality of life. Psoriasis is a chronic autoimmune condition managed with topical therapies, phototherapy, and systemic drugs. Scabies is a contagious infestation treated with permethrin and hygiene measures. Eczema is a chronic inflammatory condition managed with moisturizers, topical steroids, and avoidance of triggers.

As healthcare professionals, we have a responsibility to educate patients about their skin conditions, recognize red flags, and ensure appropriate referral when needed. Early diagnosis and proper management of skin disorders can significantly improve patient outcomes and quality of life.

As I always tell my students: “The skin is the mirror of health. Treat every patient with care, and never underestimate the impact of skin conditions on quality of life.”

REFERENCES AND FURTHER READING

• Kasper, D. L., Fauci, A. S., Hauser, S. L., et al. (2020). Harrison’s Principles of Internal Medicine (21st ed.). McGraw-Hill.
• Bolognia, J. L., Schaffer, J. V., & Cerroni, L. (2018). Dermatology (4th ed.). Elsevier.
• Lebwohl, M. G., Heymann, W. R., & Berth-Jones, J. (2020). Treatment of Skin Disease: Comprehensive Therapeutic Strategies (5th ed.). Elsevier.
• National Institute for Health and Care Excellence (NICE). (2022). Clinical Guidelines on Psoriasis, Scabies, and Eczema. Retrieved from https://www.nice.org.uk
• World Health Organization (WHO). (2022). Skin Health Resources. Retrieved from https://www.who.int

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for diagnosis and treatment.