Wool is a natural fiber valued for its warmth, moisture-wicking properties, and breathability. Merino wool is particularly prized for its exceptionally fine, soft texture. Many people report experiencing discomfort, itchiness, and skin irritation when wearing wool garments. While discomfort from wool is a widespread experience, the underlying cause is often misunderstood and is rarely a true immunological allergy.
Distinguishing True Allergic Reactions From Irritation
The reaction many people attribute to a “wool allergy” is typically a non-immunological sensitivity known as irritant contact dermatitis. This reaction is a physical response to the fiber itself, resulting in localized symptoms like itching, redness, or a rash where the fabric touches the skin. This is not a true allergy, as it does not involve the immune system creating antibodies.
A true allergy is a Type I hypersensitivity where the immune system overreacts to a specific protein, releasing chemicals like histamine. Symptoms are systemic and may include hives, swelling, difficulty breathing, or a widespread rash. Allergies to the keratin protein that makes up the wool fiber are extremely rare.
If a genuine allergic reaction is suspected, it is more likely an allergy to lanolin, a natural wax found in sheep’s wool. Modern processing removes most lanolin, and the incidence of lanolin allergy is low. The discomfort experienced by most people reacting to wool is overwhelmingly physical irritation.
Factors That Trigger Skin Sensitivity to Wool
The primary factor triggering skin sensitivity to wool is the physical dimension of the fibers, often referred to as the “prickle factor.” When a wool fiber’s diameter is too large, the rigid end of the fiber cannot bend when pressed against the skin. Instead, it pokes into the epidermis, stimulating nerve endings called nociceptors, which the brain interprets as an uncomfortable, prickly sensation.
Irritation typically correlates with fibers having a diameter greater than 30 to 32 micrometers (µm). Merino wool is significantly finer, often ranging from 15 µm to 23 µm, which is why it is considered softer and better tolerated, especially the “superfine” varieties. However, if a Merino garment contains coarser fibers exceeding the 30 µm threshold, it can still cause irritation, especially for sensitive skin.
Another element is secondary chemical irritants retained in the garment. These may include residues from dyes, cleaning agents, or various chemical finishes used during the manufacturing and processing of the wool. Although modern processing reduces these residues, they can still cause chemical contact dermatitis in some users.
Practical Steps for Relief and Prevention
For immediate relief from skin irritation caused by wool, the affected area should be washed gently with a mild soap to remove any residual fiber fragments or chemical irritants. Applying a soothing emollient or moisturizing cream can help restore the skin barrier and reduce redness and itching. For persistent or severe irritation, a mild corticosteroid cream or an oral antihistamine may be used after consulting a healthcare professional.
Prevention starts with careful garment selection, focusing on superfine Merino wool garments with the lowest possible fiber diameter. The softest wools, often labeled as “next-to-skin” layers, are processed to ensure their fiber diameter is well below the irritation threshold. Washing a new wool garment before wearing it can also help remove any remaining processing chemicals that might be contributing to the discomfort.
To soften a wool garment over time, some individuals find success by soaking the item in a solution of water mixed with white vinegar or a small amount of hair conditioner. For individuals who remain highly sensitive, wearing a thin, non-irritating layer of cotton or silk underneath the wool creates a physical barrier. If all wool causes discomfort, alternatives like Tencel or specialized synthetic fibers offer similar performance characteristics without the fiber rigidity that causes irritation.