Why do small holes appear in underwear fabric after a few washes?

Short answer: Small holes after a few washes usually have an identifiable cause: needle damage during sewing, weak or broken yarns from knitting, chemical damage from bleach or other substances, or mechanical damage from zips, hooks or rough surfaces. The location and shape of the holes are the best clues. Holes close to seams and waistbands often point to sewing; scattered holes in the body point to fabric, chemicals or care. A structured investigation is needed before changing the fabric.

Reading the holes

• Holes in a line along a seam or next to elastic: often needle damage, where the sewing needle cut or weakened yarns, which then run open after washing.
• Isolated holes with frayed edges in the body: possible yarn defects, knitting faults or mechanical snags.
• Areas where the fabric looks thin, brittle or discoloured: possible chemical damage, such as chlorine bleach or other oxidising products.
• Holes at points of contact with belts or rough seating: wear and abrasion.

Production causes and controls

Needle damage is more likely with fine, dense or elastane-rich knits when the needle is too thick, blunt or the wrong point type, or when the fabric lacks proper lubrication. Factories control it by choosing ball-point needles suited to knits, changing needles regularly and checking seams under stretch. Knitting faults such as dropped or broken stitches should be caught in fabric inspection. Inspection under ISO 2859-1 sampling can include stretching seams and checking for broken yarns.

How to investigate

• Collect several complaint garments and photograph the holes with their positions.
• Check retained garments from the same lot by stretching seams and inspecting under good light.
• Wash retained garments using the label's instructions and inspect again.
• If chemical damage is suspected, ask a laboratory to examine the fabric.

Preventing recurrence

Agree needle type and change frequency with the factory, add a stretch-and-light check on seams during inspection, and require fabric inspection for knitting defects. Clear care advice helps with bleach and abrasive laundry.

Limits

Some causes are outside the product's control, such as bleach use or snagging on other laundry. Patterns across many garments and lots are more reliable than individual reports.

Facts, recommendations and uncertainty

Established: hole location and shape point to sewing, knitting, chemical or wear causes. Recommendation: investigate retained garments before changing fabric. Uncertain: the specific cause until garments are examined.

Sources and further reading

• ISO 6330:2021 — Domestic washing and drying procedures for textile testing
• ISO 12945-2:2020 — Pilling, fuzzing or matting, modified Martindale method
• ISO 2859-1:2026 — Sampling procedures for inspection by attributes (AQL)

Standards and regulations are referenced by their published scope. Test parameters, cycles and pass levels should be agreed with your laboratory for the specific product; legal requirements should be confirmed for each destination market.