Application Technique

• How the extensions are applied greatly predicts whether they will damage the hair. Sew-in extensions using the cornrow method is very safe, but using glue to apply tracks to the natural hair can cause damage.
  
  

Maintenance

• Even a quality hair extension application can become damaging when it's not kept up well. Extensions must be brushed and washed regularly to prevent matting of natural hair underneath and tangling at the ends.
  
  

Length of Time Worn

• Each kind of hair extension is meant to be worn for a certain period of time. Leaving it in the hair too long can cause damage to the natural hair.
  
  

Removal of Extensions

• Some extensions must be removed by a professional stylist, as is the case with fusion or bonding methods. Trying to take them out yourself could damage your hair.
  
  

The Condition of Your Natural Hair

• Even if extensions are applied correctly, they can still be harmful to your hair if it's damaged or fragile. For instance, the cornrows with sew-in extensions are usually harmless but can damage fragile hair, especially around the hairline.