I’m sorry to hear that. Those are two different things, but both are being studied.
Most lactose intolerance is due to a sensitivity to a certain protein. Depending upon severity you can actually have milk, so long as it is of a type that removes or breaks down that protein. However, it is possible to survive without milk. Living without it in food is more difficult. There are lovely lactose free mills now. And I highly recommend pea protein milk. It is delicious, thick and creamy, and exceptionally good for you. High on protein, it contains no lactose of any kind. It also comes in several flavors and is far less likely to cause an allergic response, than say almond, spy, or other nut protein milk substitutes.
Speaking to food allergies: there are a number of studies being done on what causes them and how to stop them. I suppose you’ll have to be patient. What I can tell you is that the histamine response is arbitrary, archaic, and directly linked to the immune system.
There are several known treatments but all are drastic and therefore reserved for life or death allergies. You might want to see about types of exposure therapy, that introduce a bit at a time over extended periods in order to Reacclimate the body to it.