Researchers from McGill University have found that applying ice after an injury eases pain in the first few hours but may slow down recovery and prolong painful sensations. The study results were published in the journal Anesthesiology.
Cold compresses have been considered one of the primary first-aid treatments for sprains, bruises, and other soft tissue injuries for several decades. The common belief is that ice reduces inflammation and swelling, thus promoting faster healing. However, this new study challenges that practice.
A team from the Alan Edwards Centre for Research on Pain conducted experiments on mice to determine how cooling affects the recovery process. In two injury models—one involving chemically induced inflammation and another involving muscle damage from intense physical exertion—ice indeed quickly relieved pain and reduced swelling. But then an unexpected effect emerged.
In animals that received cryotherapy, soreness persisted for over 30 days, whereas mice that went untreated recovered in about 15 days.
According to lead author Lucas Lima, the results point to a paradox: methods that reduce inflammation and alleviate pain in the short term may disrupt biological processes essential for full recovery.
The researchers discovered that neutrophils play a key role in healing—these immune cells are the first to arrive at the injury site and initiate tissue repair. Cooling appears to impair their function. When scientists artificially introduced neutrophils into a cooled limb, the prolonged pain disappeared within the usual timeframe.
The authors emphasize that the results have so far only been obtained in animals, so they cannot be directly applied to humans. However, clinical trials involving people have already begun. If the data are confirmed, the conventional approach to treating injuries may change. Ice can still provide rapid relief, but that relief might come at the cost of a longer recovery period.
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