What is the difference between a strand test and a patch test?

• A. Strand test checks hair reaction to color on a strand; patch test checks skin reaction to dye ingredients
• B. Strand test checks skin reaction; patch test checks hair color changes on a strand
• C. Strand test is performed only after a positive patch test
• D. Patch test evaluates hair porosity

Answer: (A)

A strand test checks how the hair takes color on a strand, previewing the shade, how it develops, and whether the hair can tolerate the processing without damage. A patch test, in contrast, looks at the skin’s reaction to the dye ingredients by applying a small amount to the skin and watching for irritation or an allergic response over 24–48 hours. This distinction matters because the strand test helps ensure the color result and hair condition, while the patch test helps protect the client from potential skin allergies before applying dye to the scalp.