Fester vs Purulent - What's the difference?

As a verb fester

is to become septic; to become rotten.

(medicine) consisting of pus, or matter; partaking of the nature of pus; attended with suppuration; as, purulent inflammation.

(en verb)

To become septic; to become rotten.

* Milton

Wounds immedicable / Rankle, and fester , and gangrene.

To worsen, especially due to lack of attention.

Deal with the problem immediately; do not let it fester .

* Macaulay

Hatred festered in the hearts of the children of the soil.

To cause to fester or rankle.

* Marston

For which I burnt in inward, swelt'ring hate, / And fester'd rankling malice in my breast.

* ----

(Webster 1913)

(en adjective)

(medicine) Consisting of pus, or matter; partaking of the nature of pus; attended with suppuration; as, purulent inflammation.

* (English Citations of "purulent")

* mucopurulent