An Intralesional Corticosteroid Injection (ILI), commonly called a cortisone shot, is a medical procedure for severe acne. A healthcare professional injects a small, diluted amount of corticosteroid medication directly into a large, inflamed lesion. This treatment is reserved for deep, painful, inflammatory acne, such as cysts or nodules, that do not respond to standard topical or oral medications. This precise approach offers a fast-acting solution by bypassing the need for the drug to travel through the bloodstream to reach the site of inflammation.
How Cortisone Injections Target Severe Acne
The effectiveness of this treatment comes from the anti-inflammatory properties of the corticosteroid, typically a diluted form of triamcinolone acetonide. Once injected, the medication immediately suppresses the local immune response causing swelling and pain.
The steroid inhibits inflammatory cells and reduces chemical messengers, like prostaglandins and cytokines, that increase inflammation and blood flow. This rapidly slows the inflammatory cascade responsible for the size, redness, and tenderness of the nodule. Addressing the inflammation directly helps prevent the tissue damage that often leads to permanent scarring.
The Timeline of Visible Reduction
The most immediate effect is a rapid reduction in pain and deep tenderness, often beginning within a few hours of the injection. Although the lesion may appear slightly more swollen immediately after the procedure due to the injected fluid, this minor effect subsides quickly.
The primary visible reduction in size and flattening occurs within the first 24 to 48 hours. During this time, the anti-inflammatory action causes the hard, raised bump to shrink noticeably as swelling dissipates. For many patients, the lesion is significantly flatter, less red, and less prominent after two days.
By 72 hours, the lesion has undergone the bulk of its reduction in size and is no longer an active bump. While the inflammatory swelling is gone, a residual red or dark mark (post-inflammatory erythema or hyperpigmentation) may remain. This temporary discoloration can take additional time to fade completely.
Short-Term Side Effects and Follow-Up Care
Cortisone injections carry a few localized, short-term side effects. One common temporary side effect is skin atrophy, which appears as a slight dimpling or depression at the injection site. This happens because the corticosteroid can cause a temporary breakdown of collagen and fat tissue beneath the skin.
This depression is transient, and the skin returns to its normal texture within a few weeks to several months as the tissue regenerates. Another possible effect is a temporary change in skin color, manifesting as either hypopigmentation (lightening) or hyperpigmentation (darkening). These color changes improve over time without intervention.
Following the procedure, gentle care is required to support healing and minimize complications. Patients should avoid touching, squeezing, or manipulating the treated area. It is recommended to avoid applying makeup or harsh topical products to the site for at least the first 24 hours. The skin at the injection site is sensitive to the sun, so applying broad-spectrum sunscreen is advised to prevent further discoloration or irritation.