Loose Dreads

My dreads are nearly three months old, and I had refrained from washing them for a month and a half, which really helped them lock up. However, when I returned from my missions trip in Nairobi Kenya (where I was working in the slums, and walking through very dusty areas) I knew my dreads needed to be washed. Now they're soft and loose again - is there any way I can prevent this? I was planning on swimming and then washing them during the summer, but not if this is is the result . . . will my dreads always do this when I get them wet, even when they're older?

Thanks!

updated by @alyssa-j: 01/13/15 09:04:07PM

That's a good question, mine have done the same since i have been washing them weekly. Yet I also think they are suppossed to get soft as part of the process. I spent about a month without washing when i first started and it was torturous,then i been washing every week, yeah they are looser but as time progresses many of them are getting tightergetting bumps and shrinking.Not judgement, but I will not go without washing again, my scalp is much healthier now that I wash regularly.

I know your hair must be clean to dread so washing reguarly is a must.