CRYOTHERAPY

1) Pigmented lesions like solar lentigo.
2) Pre-cancerous lesions like “actinic keratosis.
Cryotherapy for melanocytic nevi generally is not recommended because could make the differentiation of benign from malignant melanocytic lesions difficult.
3) Lesions due to viral infections like warts and molluscum contagiosum.
4) Vascular lesions like Kaposi sarcoma and hemangioma.
5) Benign cysts and tumors like milia, skin tags and Seborrheic keratosis.
6) Hypertrophic scars and keloids.

In this procedure liquid nitrogen or rarely oxygen and hydrogen used to freeze the lesion. The mechanism of action in cryotherapy can be divided into 3 phases: (1) heat transfer, (2) cell injury, and (3) inflammation.

Heat transfer: The mechanism by which cryotherapy destroys the targeted cells is the quick transfer of heat from the skin to a heat sink. The most commonly used cryogen is liquid nitrogen, which has a boiling point of -196°C.

Cell injury: The transformation of water to ice concentrates the extracellular solutes and results in an osmotic gradient across the cell membrane, causing further damage. Rapid freezing and slow thawing maximize tissue damage to epithelial cells and is most suitable for the treatment of malignancies. Fibroblasts produce less collagen after a rapid thaw may be more suitable for the treatment of keloids or benign lesions in areas prone to scarring.

Inflammation: The last response to cryotherapy is inflammation, which is usually observed as erythema and edema. Inflammation is the response to cell death and helps in local cell destruction. Thorough cryotherapy treatment causes basement membrane separation, which may result in blister formation. 

1) Acute complications include headache, pain, and blister formation.
2) Delayed complications include hemorrhage, infection, and excessive granulation tissue formation.
3) Permanent complications include alopecia, atrophy, keloids, scarring, hypo pigmentation, and ectropion formation. It's more common in dark skinned people.

Contraindications can be divided into 2 groups: relative contraindications and absolute contraindications.

Relative contraindications
Include: cold intolerance, cold urticaria, cryoglobulinemia or any other disease with an increased level of, cry globulin like active ulcerative colitis and collagen-vascular diseases, history of Raynaud disease, use of cryotherapy near the eye margins.

Absolute contraindications
Include: identified hyper sensitivity, vital unexpected reactions against cryotherapy, high risks of hypo pigmentation, malignancies like melanoma and SCC, lesions with low blood supply and non-diagnostic lesions that needs biopsy for definite diagnosis.

- In young children and old people because of high risk of scar and blister formation.
- In diabetic because of lack of proper wound healing after the procedure.
- Dark skinned people because of high risk of hypo pigmentation.
- In injured skin (caused by solar radiation or topical corticosteroids), because of high risk of blister formation and necrosis.
- In pregnancy, because of increased level of cry globulin.