Can scratching spread psoriasis?

Can Scratching Spread Psoriasis?

Yes, scratching can spread psoriasis through a process called the Koebner phenomenon, where new psoriatic lesions develop at sites of skin trauma or injury. 1

Understanding the Koebner Phenomenon

The Koebner phenomenon is a well-documented process in psoriasis where physical trauma to the skin triggers the development of new psoriatic lesions in previously unaffected areas. This occurs through several mechanisms:

• Scratching damages the epidermis, triggering the release of chemokine (C-C motif) ligand 20 (CCL20) from keratinocytes 2
• CCL20 attracts IL-17A-producing immune cells to the injured site 2
• This inflammatory cascade leads to the development of new psoriatic plaques 3

Scratching is one of several triggers that can induce the Koebner phenomenon, alongside other forms of trauma such as:

• Friction from tight clothing
• Skin incisions
• Tattoos
• Radiation
• Viral infections 3

Clinical Evidence and Implications

Research has demonstrated that the Koebner phenomenon occurs in a significant percentage of psoriasis patients:

• In experimental studies, approximately 25-30% of psoriasis patients develop new lesions at sites of controlled skin trauma 4
• Koebnerization of the scalp due to repetitive scratching can lead to unilateral, well-circumscribed hypertrophic plaques that are particularly resistant to therapy 1

Management Recommendations

To prevent the spread of psoriasis through scratching:

1. Address underlying pruritus:

   • Identify and treat the cause of itching
   • Consider that stress and psychological factors can worsen pruritus 1

2. Break the itch-scratch cycle:

   • Apply appropriate topical treatments based on location and severity 1, 5
   • For intertriginous areas, use lower potency corticosteroids to minimize irritation 1
   • Consider emollients like petrolatum after bathing to reduce friction and irritation 1

3. Patient education:

   • Explain the Koebner phenomenon and how scratching can lead to new lesions 1
   • Teach patients about avoiding trigger factors including mechanical trauma 1
   • Emphasize the importance of stress management techniques 1

Special Considerations

• Scalp psoriasis: This area is particularly prone to Koebnerization from scratching and can be especially difficult to treat 1
• Inverse psoriasis: Friction and irritation play significant roles in this subtype; emollients are particularly beneficial 1
• Psychological factors: Stress can worsen both pruritus and psoriasis; addressing psychological factors is important 1

Common Pitfalls to Avoid

• Underestimating the impact of scratching: Even minor trauma can trigger new lesions in susceptible individuals 3
• Focusing only on visible lesions: Patient education about avoiding scratching is equally important to topical treatments 1
• Ignoring psychological factors: Stress management should be incorporated into treatment plans 1

Remember that while scratching can spread psoriasis through the Koebner phenomenon, appropriate treatment of existing lesions and prevention of trauma through patient education are key components of effective management.