Nicole,
To say that once you have ABPA, you always have it is a bit presumptuous. ABPA is not well understood since it is not easily studied. ABPA is dependent on 2 things, your being exposed to aspergillus (or culturing it even) and also having an allergic reaction to it. While it's true that those of us with ABPA will likely always be hypersensitive to aspergillus, we may not always be culturing it or exposed to it. Therefore a Dx of ABPA does not mean that it's going to be a constant problem for you. Also, there are quite a few people who culture aspergillus and do not have a hypersensitivity to it.
Until more is learned about ABPA high dose steroids will probably remain the standard of care. If you reference the questions asked by Zara and Lilywing they were inquiring about prevention and alternatives to treatment with steroids, which i think is a very valid question given the problems associated with high dose or long term corticosteroid use.
As most of us mentioned removing sources of aspergillus from your environment is the best method of prevention. As far as alternatives to steroids Xolair is the only one I am familiar with. Xolair is, in fact, for SC injection. However it's dosing schedule is based on total serum IgE and weight. Your dose was likely over 150mg, which left your physician with 2 choices, use multiple sites (up to 3), which would have resulted in multiple injections, or give then entire dose IM, which can accommodate larger volumes. It seems in your case that they went the IM route, although I was unable to locate any literature that advocated IM injection. Usually IM v. SC isn't an issue unless rate of absorption is a factor. Xolair was associated with some cases of anaphylaxis in clinical trials which is probably why they chose the slower absorption of the SC route. Since you were being treated by an allergist they may have been more comfortable giving it IM and treating any reaction should it on the off chance occur. Saying that it is not a SC injection is very misleading, as for some people it very well may be a SC injection if their dose is 150mg, or multiple SC injections if their dose is higher than 150mg and their physician decides to play by the books.