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If the strings are in the area of the tenderness in the muscle layer, they are likely from tightened muscle fibers related to the muscle problem, such as a muscle strain. It is also possible that a string sensation could be related to inflammation, and if it is is the skin layer, rather than the muscle layer, this would be more likely. In either case, they will typically diminish as the underlying cause improves.
It is common to get itching of the skin associated with liver disease, including liver disease associated with alcohol consumption. When this happens, it would not be surprising if the itching is worse after ingestion of alcohol. Itching also is common with eczema, and it is possible for eczema to be worse from alcohol consumption, but this is less common than worsening of liver symptoms from alcohol consumption. However, the evaluation of the liver will provide a better picture of his liver status.
For tenderness in the muscle layer, there are a couple of options. The most commonly used would be one of the anti-inflammatory medicines, such as ibuprofen or naproxen, although GI irritation is a common side effect to these medicines. It also may help to use a muscle relaxer, but these are only available by prescription and you do not say whether he has been tried on a muscle relaxer. It also may help to apply moist heat to the abdominal wall, which has a direct effect on reducing inflammation.