What Causes the Body to Reject the Stitches?

There are a variety of suture materials available and you may be "rejecting" them for several different reasons.
Sometimes it is an immune response that can be triggered from multiple previous exposures in past surgery.
Alternatively a variety of different chemicals are now being added to sutures as antibiotics to minimize the possibility of infection. This also can cause reactions.
When sutures get contaminated, the structure of the material itself can also cause different reactions. A braided suture material is more likely to react and hold bacteria than a single stranded suture (monofilament).
Placement of the suture too close to the surface can also cause the suture to erode to the surface.
Some longer lasting sutures get ejected from the body the same way a splinter gets ejected from the skin.
As you can see there are many factors that can cause a suture to be rejected.

Thank you for your question regarding the body’s potential to reject stitches after surgery. Stitch rejection, or more accurately, a suture reaction, can happen when the body has an adverse reaction to the material used in the stitches. This is rare but can occur with both absorbable and non-absorbable sutures.

Here are a few common causes of stitch rejection:

Allergic reaction: The body may have an allergic reaction to certain suture materials, especially if they are synthetic or foreign to the body.
Infection: Sometimes, an infection can develop around the sutures, causing the body to react and push the sutures out to prevent further complications.
Body’s healing response: In some cases, the body sees the stitches as a foreign object and tries to expel them as part of the healing process. This can result in the stitches working their way out of the skin, which can be uncomfortable.
The symptoms of stitch rejection include:

Redness or irritation around the sutures
Swelling or oozing near the stitch site
Stitch material becoming visible on the surface or "spitting" through the skin
If you’re experiencing discomfort from a reaction to the stitches, here’s what can be done:

Consult your surgeon: If you suspect a suture reaction or infection, it’s important to contact your surgeon right away. They may decide to remove the problematic stitches.
Topical treatments: Your doctor may recommend topical antibiotics or steroid creams to reduce inflammation and irritation.
Wound care: Keeping the area clean and dry can prevent infection and reduce the severity of the reaction.
In terms of how long you can expect to experience discomfort, it depends on the severity of the reaction. Mild cases may resolve in a few weeks as the body absorbs the sutures or they are removed. Severe cases may require medical attention to remove the stitches and treat any infection or irritation.

I recommend consulting with your plastic surgeon to assess your situation and provide relief. If the stitches are causing significant discomfort or complications, your surgeon can help determine the best course of action.

Sincerely,
Dr. Katzen

Stitches "spit" when the ends of the suture are too close to the skin edge. As healing occurs and the wound contracts the knot and ends of the stitches get close to and break the skin surface cause them to "spit." I suspect that if you have multiple spitting sutures it's because your surgeon did interrupted stitches along the incision line with significant knots. If you're out 6 weeks or more he should remove them as they spit then consider using different suture or a running stitch next time.

You need to give more information as to what is going on. What are you suffering from? What do you mean by rejection? Where on your body and when was your surgery?