Healing of skin wounds: first and second intention !

Process

A clean cut with edges brought together heals fast with a thin scar; an open wound fills from the bottom up, shrinks and leaves a bigger scar.

Updated 2026-11-01

What it is

Skin wounds heal in overlapping phases: haemostasis, inflammation, proliferation and remodelling. Healing by first (primary) intention happens when the edges are close, as in a sutured surgical incision. Healing by second (secondary) intention happens in large, open or infected wounds, which need more granulation tissue and contract. A third route, delayed primary closure, is used for contaminated wounds. The timeline explains when sutures come out and when a wound is weakest.

Step by step

First hours: the incision fills with clot; neutrophils reach the edges within 24 hours.
24–48 hours: basal epidermal cells from both edges migrate and proliferate, covering the cut with a thin epithelial layer.
Day 3: macrophages replace neutrophils and granulation tissue begins to invade the incision space.
Day 5: granulation tissue fills the gap; new vessel formation peaks and collagen fibrils begin to bridge the incision.
Week 2: collagen keeps accumulating, vessels and oedema decrease, and the scar starts to blanch.
End of month 1: a scar of collagen with few cells, covered by intact epidermis; hair follicles and glands along the line are lost.
Following months: remodelling; strength rises from about 10% at suture removal to about 70–80% by three months.

First vs second intention

Feature	First intention	Second intention
Typical wound	Clean surgical incision with edges brought together	Large, gaping, infected or ulcerated wound left open
Inflammation	Limited	More intense (more debris, fibrin, infection)
Granulation tissue	Little	Abundant; fills the defect from the base
Wound contraction	Minimal	Marked, by myofibroblasts
Scar	Thin line	Larger; may cause contracture
Time	Shorter	Longer

Clinical notes

Delayed primary (tertiary) closure: a contaminated wound is left open for a few days, cleaned and then sutured.
Wound dehiscence is most common in the first one to two weeks, when strength is lowest; risk rises with infection, obesity, coughing, vomiting, malnutrition and glucocorticoids.
A healed wound never regains full strength, which is why incisional hernias can appear months or years later.

Test yourself

Think of the answer, then tap the question to see it.

Which cells drive wound contraction in healing by second intention?

Myofibroblasts, fibroblasts with contractile filaments of alpha-smooth muscle actin.

About how strong is a wound, compared with normal skin, when sutures are removed at one week?

About 10%; it reaches roughly 70–80% by three months and never returns to 100%.

When is a surgical wound most likely to dehisce?

In the first one to two postoperative weeks, before enough collagen has been deposited and cross-linked.

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