Properly made colloidal silver will not harm you, and I would not consider 50ppm to be a high dose.
The biggest issue with colloidal silver is that it is expensive to buy, and due to competition between manufacturers, everyone insists they make the best product while the others aren't true colloidal silver, or don't contain the strength in ppm that it states on the bottle, etc.
The best solution is one you make yourself, using a high quality silver generator. This could cost around $400 but at $40 per small bottle it would pay for itself in no time.
You start with distilled water, at zero parts per million, and finish with a 20ppm solution, that you know is pure ionic silver with very small positively charged ions. You can safely take up to 4 ounces per day for years because the body has the ability to excreet excess silver, mostly through the urine...which also means no urinary tract infections.
There are several silver generators on the market, and most are fine. The one I chose was from www.silverlungs.com
because the unit is totally closed in so there is little chance of contamination, makes either 10 or 20 ppm solution as per switch setting, comes with 7 gauge pure silver rods, which are thicker than any other product that I've seen, comes with an electronic stir device, and is very quiet and professional.
I don't get anything for recommending this product, I do so because its the best, and the way things are heading with antibiotic resistant bacteria, viruses, and fungal issues, I would suggest everyone own one of these silver generators.
I bought one of these units several years ago, still make a batch every week, and don't get colds or flu.